drivers: small fixes for low-level pwm driver IF
drivers: small fixes for low-level pwm driver IF

- added UNDEFINED device for compatability
- adjusted meaning of return values for init and set functions
- overdue spell fix

shady33/RIOT,kerneltask/RIOT,shady33/RIOT,automote/RIOT,DipSwitch/RIOT,rfuentess/RIOT,ThanhVic/RIOT,lazytech-org/RIOT,backenklee/RIOT,mtausig/RIOT,binarylemon/RIOT,Darredevil/RIOT,rajma996/RIOT,avmelnikoff/RIOT,koenning/RIOT,centurysys/RIOT,centurysys/RIOT,sumanpanchal/RIOT,arvindpdmn/RIOT,altairpearl/RIOT,ntrtrung/RIOT,sgso/RIOT,jfischer-phytec-iot/RIOT,gebart/RIOT,roberthartung/RIOT,robixnai/RIOT,locicontrols/RIOT,dhruvvyas90/RIOT,rousselk/RIOT,herrfz/RIOT-old,spium/IoT-RIOT,authmillenon/RIOT,ximus/RIOT,jremmert-phytec-iot/RIOT,Hyungsin/RIOT-OS,kYc0o/RIOT,rajma996/RIOT,neiljay/RIOT,AnonMall/RIOT,thomaseichinger/RIOT,abkam07/RIOT,rfswarm/RIOT,neiljay/RIOT,LudwigOrtmann/RIOT,fnack/RIOT,Ell-i/RIOT,AnonMall/RIOT,Osblouf/RIOT,emmanuelsearch/RIOT,neumodisch/RIOT,rfswarm2/RIOT,latsku/RIOT,wentaoshang/RIOT,patkan/RIOT,rakendrathapa/RIOT,jremmert-phytec-iot/RIOT,emmanuelsearch/RIOT,MarkXYang/RIOT,rfswarm2/RIOT,l3nko/RIOT,watr-li/RIOT,chris-wood/RIOT,LudwigKnuepfer/RIOT,benoit-canet/RIOT,yogo1212/RIOT,mtausig/RIOT,RubikonAlpha/RIOT,arvindpdmn/RIOT,tfar/RIOT,basilfx/RIOT,chris-wood/RIOT,rajma996/RIOT,altairpearl/RIOT,TobiasFredersdorf/RIOT,rakendrathapa/RIOT,ros2/ros2_embedded_riot,adrianghc/RIOT,Darredevil/RIOT,josephnoir/RIOT,gbarnett/RIOT,fnack/RIOT,JensErdmann/RIOT,miri64/RIOT,benoit-canet/RIOT,daniel-k/RIOT,BytesGalore/RIOT,sumanpanchal/RIOT,wentaoshang/RIOT,rfswarm2/RIOT,mfrey/RIOT,Darredevil/RIOT,tdautc19841202/RIOT,dhruvvyas90/RIOT,BytesGalore/PetersRIOT,kaspar030/RIOT,jferreir/RIOT,rousselk/RIOT,kerneltask/RIOT,TobiasFredersdorf/RIOT,chris-wood/RIOT,jremmert-phytec-iot/RIOT,DipSwitch/RIOT,msolters/RIOT,ThanhVic/RIOT,gbarnett/RIOT,herrfz/RIOT,alignan/RIOT,centurysys/RIOT,Osblouf/RIOT,watr-li/RIOT,Lexandro92/RIOT-CoAP,cladmi/RIOT,EmuxEvans/RIOT,locicontrols/RIOT,FrancescoErmini/RIOT,marcosalm/RIOT,rousselk/RIOT,gebart/RIOT,mfrey/RIOT,automote/RIOT,ntrtrung/RIOT,katezilla/RIOT,adjih/RIOT,alex1818/RIOT,neumodisch/RIOT,Hyungsin/RIOT-OS,emmanuelsearch/RIOT,MarkXYang/RIOT,DipSwitch/RIOT,FrancescoErmini/RIOT,basilfx/RIOT,kushalsingh007/RIOT,cladmi/RIOT,shady33/RIOT,sumanpanchal/RIOT,ntrtrung/RIOT,EmuxEvans/RIOT,herrfz/RIOT,l3nko/RIOT,binarylemon/RIOT,josephnoir/RIOT,MarkXYang/RIOT,kushalsingh007/RIOT,zhuoshuguo/RIOT,TobiasFredersdorf/RIOT,shady33/RIOT,tdautc19841202/RIOT,asanka-code/RIOT,smlng/RIOT,koenning/RIOT,stevenj/RIOT,JensErdmann/RIOT,alex1818/RIOT,herrfz/RIOT,abp719/RIOT,phiros/RIOT,DipSwitch/RIOT,d00616/RIOT,mtausig/RIOT,RubikonAlpha/RIOT,smlng/RIOT,kYc0o/RIOT,plushvoxel/RIOT,emmanuelsearch/RIOT,kerneltask/RIOT,abkam07/RIOT,zhuoshuguo/RIOT,robixnai/RIOT,josephnoir/RIOT,ximus/RIOT,malosek/RIOT,locicontrols/RIOT,neiljay/RIOT,ThanhVic/RIOT,ros2/ros2_embedded_riot,Hyungsin/RIOT-OS,jhollister/RIOT,watr-li/RIOT,tfar/RIOT,rfuentess/RIOT,backenklee/RIOT,altairpearl/RIOT,herrfz/RIOT-old,ximus/RIOT,khhhh/RIOT,luciotorre/RIOT,MohmadAyman/RIOT,dkm/RIOT,Hyungsin/RIOT-OS,asanka-code/RIOT,d00616/RIOT,locicontrols/RIOT,josephnoir/RIOT,foss-for-synopsys-dwc-arc-processors/RIOT,tfar/RIOT,alex1818/RIOT,Lexandro92/RIOT-CoAP,lazytech-org/RIOT,kaleb-himes/RIOT,A-Paul/RIOT,BytesGalore/RIOT,Josar/RIOT,latsku/RIOT,plushvoxel/RIOT,binarylemon/RIOT,biboc/RIOT,sgso/RIOT,hamilton-mote/RIOT-OS,thiagohd/RIOT,MohmadAyman/RIOT,Lotterleben/RIOT,daniel-k/RIOT,asanka-code/RIOT,stevenj/RIOT,FrancescoErmini/RIOT,dkm/RIOT,thomaseichinger/RIOT,kaspar030/RIOT,dhruvvyas90/RIOT,syin2/RIOT,changbiao/RIOT,1blankz7/RIOT,robixnai/RIOT,Darredevil/RIOT,rfswarm2/RIOT,PSHIVANI/Riot-Code,gebart/RIOT,Lotterleben/RIOT,MohmadAyman/RIOT,openkosmosorg/RIOT,neumodisch/RIOT,daniel-k/RIOT,alignan/RIOT,BytesGalore/PetersRIOT,shady33/RIOT,jasonatran/RIOT,authmillenon/RIOT,JensErdmann/RIOT,Ell-i/RIOT,mziegert/RIOT,smlng/RIOT,biboc/RIOT,l3nko/RIOT,beurdouche/RIOT,lebrush/RIOT,authmillenon/RIOT,immesys/RiSyn,robixnai/RIOT,zhuoshuguo/RIOT,abp719/RIOT,immesys/RiSyn,MonsterCode8000/RIOT,neumodisch/RIOT,altairpearl/RIOT,adrianghc/RIOT,kb2ma/RIOT,A-Paul/RIOT,biboc/RIOT,avmelnikoff/RIOT,lebrush/RIOT,basilfx/RIOT,EmuxEvans/RIOT,luciotorre/RIOT,RBartz/RIOT,bartfaizoltan/RIOT,RIOT-OS/RIOT,lazytech-org/RIOT,malosek/RIOT,openkosmosorg/RIOT,A-Paul/RIOT,beurdouche/RIOT,roberthartung/RIOT,patkan/RIOT,nsol-nmsu/RIOT,abp719/RIOT,dhruvvyas90/RIOT,BytesGalore/RIOT,changbiao/RIOT,wentaoshang/RIOT,OTAkeys/RIOT,openkosmosorg/RIOT,katezilla/RIOT,altairpearl/RIOT,PSHIVANI/Riot-Code,stevenj/RIOT,jfischer-phytec-iot/RIOT,fnack/RIOT,RIOT-OS/RIOT,LudwigOrtmann/RIOT,ThanhVic/RIOT,PSHIVANI/Riot-Code,basilfx/RIOT,jbeyerstedt/RIOT-OTA-update,x3ro/RIOT,hamilton-mote/RIOT-OS,dhruvvyas90/RIOT,benoit-canet/RIOT,arvindpdmn/RIOT,automote/RIOT,jferreir/RIOT,1blankz7/RIOT,biboc/RIOT,ros2/ros2_embedded_riot,AnonMall/RIOT,kaleb-himes/RIOT,daniel-k/RIOT,MonsterCode8000/RIOT,patkan/RIOT,khhhh/RIOT,BytesGalore/PetersRIOT,sumanpanchal/RIOT,rfuentess/RIOT,RubikonAlpha/RIOT,nsol-nmsu/RIOT,stevenj/RIOT,cladmi/RIOT,Yonezawa-T2/RIOT,LudwigKnuepfer/RIOT,attdona/RIOT,JensErdmann/RIOT,yogo1212/RIOT,nsol-nmsu/RIOT,d00616/RIOT,locicontrols/RIOT,jhollister/RIOT,kushalsingh007/RIOT,neumodisch/RIOT,herrfz/RIOT,RBartz/RIOT,malosek/RIOT,RIOT-OS/RIOT,patkan/RIOT,JensErdmann/RIOT,EmuxEvans/RIOT,TobiasFredersdorf/RIOT,phiros/RIOT,MarkXYang/RIOT,backenklee/RIOT,openkosmosorg/RIOT,ant9000/RIOT,herrfz/RIOT,Lotterleben/RIOT,aeneby/RIOT,msolters/RIOT,MonsterCode8000/RIOT,OlegHahm/RIOT,gbarnett/RIOT,rfuentess/RIOT,aeneby/RIOT,openkosmosorg/RIOT,foss-for-synopsys-dwc-arc-processors/RIOT,EmuxEvans/RIOT,thomaseichinger/RIOT,FrancescoErmini/RIOT,ximus/RIOT,rakendrathapa/RIOT,shady33/RIOT,jbeyerstedt/RIOT-OTA-update,tdautc19841202/RIOT,abkam07/RIOT,dailab/RIOT,alignan/RIOT,AnonMall/RIOT,DipSwitch/RIOT,dailab/RIOT,roberthartung/RIOT,thomaseichinger/RIOT,RubikonAlpha/RIOT,jbeyerstedt/RIOT-OTA-update,khhhh/RIOT,rajma996/RIOT,immesys/RiSyn,x3ro/RIOT,koenning/RIOT,msolters/RIOT,rajma996/RIOT,Ell-i/RIOT,ximus/RIOT,emmanuelsearch/RIOT,jfischer-phytec-iot/RIOT,Osblouf/RIOT,avmelnikoff/RIOT,alex1818/RIOT,LudwigKnuepfer/RIOT,bartfaizoltan/RIOT,syin2/RIOT,A-Paul/RIOT,watr-li/RIOT,OlegHahm/RIOT,gebart/RIOT,Lexandro92/RIOT-CoAP,stevenj/RIOT,luciotorre/RIOT,attdona/RIOT,MonsterCode8000/RIOT,RBartz/RIOT,rousselk/RIOT,haoyangyu/RIOT,khhhh/RIOT,rakendrathapa/RIOT,fnack/RIOT,sumanpanchal/RIOT,PSHIVANI/Riot-Code,LudwigOrtmann/RIOT,mziegert/RIOT,wentaoshang/RIOT,patkan/RIOT,spium/IoT-RIOT,malosek/RIOT,RIOT-OS/RIOT,toonst/RIOT,khhhh/RIOT,Lexandro92/RIOT-CoAP,cladmi/RIOT,BytesGalore/PetersRIOT,katezilla/RIOT,immesys/RiSyn,phiros/RIOT,binarylemon/RIOT,kaleb-himes/RIOT,foss-for-synopsys-dwc-arc-processors/RIOT,MarkXYang/RIOT,thiagohd/RIOT,thiagohd/RIOT,jasonatran/RIOT,JensErdmann/RIOT,malosek/RIOT,jferreir/RIOT,aeneby/RIOT,LudwigOrtmann/RIOT,rfswarm/RIOT,alex1818/RIOT,jhollister/RIOT,luciotorre/RIOT,gbarnett/RIOT,yogo1212/RIOT,authmillenon/RIOT,dailab/RIOT,sgso/RIOT,Ell-i/RIOT,dkm/RIOT,ant9000/RIOT,x3ro/RIOT,neumodisch/RIOT,AnonMall/RIOT,robixnai/RIOT,lebrush/RIOT,OTAkeys/RIOT,RBartz/RIOT,ntrtrung/RIOT,jfischer-phytec-iot/RIOT,phiros/RIOT,thiagohd/RIOT,watr-li/RIOT,changbiao/RIOT,automote/RIOT,rfswarm2/RIOT,luciotorre/RIOT,attdona/RIOT,Yonezawa-T2/RIOT,daniel-k/RIOT,sumanpanchal/RIOT,l3nko/RIOT,lebrush/RIOT,mfrey/RIOT,mziegert/RIOT,Josar/RIOT,locicontrols/RIOT,kYc0o/RIOT,adjih/RIOT,adrianghc/RIOT,toonst/RIOT,plushvoxel/RIOT,mziegert/RIOT,LudwigKnuepfer/RIOT,kushalsingh007/RIOT,miri64/RIOT,attdona/RIOT,herrfz/RIOT,zhuoshuguo/RIOT,neiljay/RIOT,luciotorre/RIOT,tfar/RIOT,roberthartung/RIOT,ThanhVic/RIOT,brettswann/RIOT,hamilton-mote/RIOT-OS,FrancescoErmini/RIOT,kushalsingh007/RIOT,RBartz/RIOT,rajma996/RIOT,centurysys/RIOT,khhhh/RIOT,adjih/RIOT,Hyungsin/RIOT-OS,mfrey/RIOT,alex1818/RIOT,kaspar030/RIOT,herrfz/RIOT-old,Osblouf/RIOT,attdona/RIOT,Lotterleben/RIOT,d00616/RIOT,sgso/RIOT,brettswann/RIOT,ant9000/RIOT,centurysys/RIOT,lazytech-org/RIOT,miri64/RIOT,rfswarm/RIOT,bartfaizoltan/RIOT,abkam07/RIOT,beurdouche/RIOT,haoyangyu/RIOT,kaleb-himes/RIOT,l3nko/RIOT,koenning/RIOT,alignan/RIOT,brettswann/RIOT,Josar/RIOT,plushvoxel/RIOT,smlng/RIOT,automote/RIOT,spium/IoT-RIOT,jremmert-phytec-iot/RIOT,aeneby/RIOT,kb2ma/RIOT,brettswann/RIOT,lazytech-org/RIOT,abkam07/RIOT,asanka-code/RIOT,yogo1212/RIOT,dkm/RIOT,malosek/RIOT,hamilton-mote/RIOT-OS,Ell-i/RIOT,rfuentess/RIOT,PSHIVANI/Riot-Code,hamilton-mote/RIOT-OS,haoyangyu/RIOT,miri64/RIOT,arvindpdmn/RIOT,alignan/RIOT,RBartz/RIOT,sgso/RIOT,jferreir/RIOT,syin2/RIOT,rfswarm2/RIOT,Lexandro92/RIOT-CoAP,marcosalm/RIOT,DipSwitch/RIOT,smlng/RIOT,kYc0o/RIOT,marcosalm/RIOT,locicontrols/RIOT,benoit-canet/RIOT,benoit-canet/RIOT,beurdouche/RIOT,dailab/RIOT,roberthartung/RIOT,rakendrathapa/RIOT,altairpearl/RIOT,bartfaizoltan/RIOT,abp719/RIOT,tdautc19841202/RIOT,BytesGalore/PetersRIOT,msolters/RIOT,avmelnikoff/RIOT,brettswann/RIOT,dailab/RIOT,fnack/RIOT,l3nko/RIOT,biboc/RIOT,kbumsik/RIOT,yogo1212/RIOT,MohmadAyman/RIOT,toonst/RIOT,emmanuelsearch/RIOT,katezilla/RIOT,spium/IoT-RIOT,wentaoshang/RIOT,backenklee/RIOT,ros2/ros2_embedded_riot,adjih/RIOT,Yonezawa-T2/RIOT,herrfz/RIOT-old,syin2/RIOT,BytesGalore/RIOT,benoit-canet/RIOT,jhollister/RIOT,zhuoshuguo/RIOT,OlegHahm/RIOT,thiagohd/RIOT,A-Paul/RIOT,brettswann/RIOT,1blankz7/RIOT,x3ro/RIOT,Yonezawa-T2/RIOT,kbumsik/RIOT,BytesGalore/PetersRIOT,gautric/RIOT,rfswarm/RIOT,kb2ma/RIOT,authmillenon/RIOT,OlegHahm/RIOT,ximus/RIOT,cladmi/RIOT,bartfaizoltan/RIOT,yogo1212/RIOT,kb2ma/RIOT,latsku/RIOT,LudwigOrtmann/RIOT,msolters/RIOT,backenklee/RIOT,marcosalm/RIOT,chris-wood/RIOT,gbarnett/RIOT,mtausig/RIOT,wentaoshang/RIOT,x3ro/RIOT,RIOT-OS/RIOT,fnack/RIOT,LudwigOrtmann/RIOT,Lotterleben/RIOT,jasonatran/RIOT,gautric/RIOT,Josar/RIOT,rfswarm/RIOT,kbumsik/RIOT,gbarnett/RIOT,arvindpdmn/RIOT,patkan/RIOT,adjih/RIOT,jferreir/RIOT,kerneltask/RIOT,authmillenon/RIOT,msolters/RIOT,haoyangyu/RIOT,ntrtrung/RIOT,gautric/RIOT,automote/RIOT,abp719/RIOT,haoyangyu/RIOT,kbumsik/RIOT,koenning/RIOT,Darredevil/RIOT,tdautc19841202/RIOT,kaspar030/RIOT,gautric/RIOT,nsol-nmsu/RIOT,chris-wood/RIOT,jbeyerstedt/RIOT-OTA-update,adrianghc/RIOT,tfar/RIOT,chris-wood/RIOT,ant9000/RIOT,asanka-code/RIOT,ks156/RIOT,aeneby/RIOT,BytesGalore/RIOT,mziegert/RIOT,OTAkeys/RIOT,miri64/RIOT,ks156/RIOT,basilfx/RIOT,RubikonAlpha/RIOT,EmuxEvans/RIOT,jasonatran/RIOT,Osblouf/RIOT,OlegHahm/RIOT,attdona/RIOT,thomaseichinger/RIOT,thiagohd/RIOT,latsku/RIOT,ant9000/RIOT,jasonatran/RIOT,rakendrathapa/RIOT,neiljay/RIOT,ks156/RIOT,daniel-k/RIOT,abp719/RIOT,zhuoshuguo/RIOT,OTAkeys/RIOT,kYc0o/RIOT,d00616/RIOT,abkam07/RIOT,plushvoxel/RIOT,FrancescoErmini/RIOT,Yonezawa-T2/RIOT,mziegert/RIOT,avmelnikoff/RIOT,jhollister/RIOT,kaspar030/RIOT,ntrtrung/RIOT,d00616/RIOT,immesys/RiSyn,josephnoir/RIOT,asanka-code/RIOT,arvindpdmn/RIOT,adrianghc/RIOT,latsku/RIOT,syin2/RIOT,Josar/RIOT,lebrush/RIOT,rfswarm/RIOT,ks156/RIOT,jferreir/RIOT,gautric/RIOT,jhollister/RIOT,latsku/RIOT,ros2/ros2_embedded_riot,centurysys/RIOT,rousselk/RIOT,ThanhVic/RIOT,tdautc19841202/RIOT,sgso/RIOT,MohmadAyman/RIOT,katezilla/RIOT,MonsterCode8000/RIOT,kbumsik/RIOT,1blankz7/RIOT,1blankz7/RIOT,marcosalm/RIOT,toonst/RIOT,MonsterCode8000/RIOT,jfischer-phytec-iot/RIOT,openkosmosorg/RIOT,herrfz/RIOT-old,bartfaizoltan/RIOT,phiros/RIOT,nsol-nmsu/RIOT,changbiao/RIOT,jbeyerstedt/RIOT-OTA-update,immesys/RiSyn,marcosalm/RIOT,jremmert-phytec-iot/RIOT,haoyangyu/RIOT,lebrush/RIOT,Lotterleben/RIOT,BytesGalore/PetersRIOT,TobiasFredersdorf/RIOT,dhruvvyas90/RIOT,watr-li/RIOT,Yonezawa-T2/RIOT,ros2/ros2_embedded_riot,MarkXYang/RIOT,binarylemon/RIOT,PSHIVANI/Riot-Code,changbiao/RIOT,foss-for-synopsys-dwc-arc-processors/RIOT,Osblouf/RIOT,ros2/ros2_embedded_riot,AnonMall/RIOT,jremmert-phytec-iot/RIOT,phiros/RIOT,OTAkeys/RIOT,kerneltask/RIOT,RubikonAlpha/RIOT,koenning/RIOT,robixnai/RIOT,toonst/RIOT,Darredevil/RIOT,mtausig/RIOT,foss-for-synopsys-dwc-arc-processors/RIOT,changbiao/RIOT,spium/IoT-RIOT,spium/IoT-RIOT,MohmadAyman/RIOT,Lexandro92/RIOT-CoAP,1blankz7/RIOT,ks156/RIOT,kushalsingh007/RIOT,beurdouche/RIOT,kb2ma/RIOT,binarylemon/RIOT,gebart/RIOT,kaleb-himes/RIOT,mfrey/RIOT,LudwigKnuepfer/RIOT,stevenj/RIOT,dkm/RIOT,rousselk/RIOT,Lotterleben/RIOT