embUnit: simplify `strcmp()` implementation
embUnit: simplify `strcmp()` implementation

The logic of `stdimpl_strcmp()` was needlessly complicated and not
understood by scan-build. This change fixes the warning and makes the
code more readable.

Found via scan-build.

A-Paul/RIOT,MohmadAyman/RIOT,LudwigOrtmann/RIOT,hamilton-mote/RIOT-OS,adjih/RIOT,ks156/RIOT,cladmi/RIOT,toonst/RIOT,altairpearl/RIOT,shady33/RIOT,l3nko/RIOT,tfar/RIOT,jremmert-phytec-iot/RIOT,syin2/RIOT,abp719/RIOT,kb2ma/RIOT,roberthartung/RIOT,avmelnikoff/RIOT,LudwigKnuepfer/RIOT,mtausig/RIOT,mziegert/RIOT,altairpearl/RIOT,tfar/RIOT,kaleb-himes/RIOT,rfuentess/RIOT,miri64/RIOT,katezilla/RIOT,foss-for-synopsys-dwc-arc-processors/RIOT,watr-li/RIOT,ks156/RIOT,hamilton-mote/RIOT-OS,cladmi/RIOT,OTAkeys/RIOT,shady33/RIOT,katezilla/RIOT,thomaseichinger/RIOT,l3nko/RIOT,gebart/RIOT,adrianghc/RIOT,adrianghc/RIOT,jbeyerstedt/RIOT-OTA-update,neiljay/RIOT,authmillenon/RIOT,TobiasFredersdorf/RIOT,TobiasFredersdorf/RIOT,adrianghc/RIOT,kaspar030/RIOT,RIOT-OS/RIOT,OTAkeys/RIOT,immesys/RiSyn,mziegert/RIOT,Ell-i/RIOT,rakendrathapa/RIOT,authmillenon/RIOT,kbumsik/RIOT,roberthartung/RIOT,stevenj/RIOT,ant9000/RIOT,msolters/RIOT,OlegHahm/RIOT,plushvoxel/RIOT,adjih/RIOT,JensErdmann/RIOT,hamilton-mote/RIOT-OS,Hyungsin/RIOT-OS,x3ro/RIOT,MonsterCode8000/RIOT,mfrey/RIOT,Ell-i/RIOT,kaleb-himes/RIOT,plushvoxel/RIOT,aeneby/RIOT,shady33/RIOT,abp719/RIOT,herrfz/RIOT,malosek/RIOT,lazytech-org/RIOT,JensErdmann/RIOT,msolters/RIOT,latsku/RIOT,katezilla/RIOT,RubikonAlpha/RIOT,wentaoshang/RIOT,kerneltask/RIOT,rakendrathapa/RIOT,ant9000/RIOT,l3nko/RIOT,latsku/RIOT,tfar/RIOT,khhhh/RIOT,stevenj/RIOT,biboc/RIOT,katezilla/RIOT,neiljay/RIOT,khhhh/RIOT,watr-li/RIOT,jasonatran/RIOT,dhruvvyas90/RIOT,msolters/RIOT,LudwigOrtmann/RIOT,rousselk/RIOT,x3ro/RIOT,asanka-code/RIOT,attdona/RIOT,altairpearl/RIOT,lebrush/RIOT,Josar/RIOT,jasonatran/RIOT,LudwigOrtmann/RIOT,MohmadAyman/RIOT,mziegert/RIOT,Hyungsin/RIOT-OS,katezilla/RIOT,josephnoir/RIOT,msolters/RIOT,rajma996/RIOT,dailab/RIOT,LudwigKnuepfer/RIOT,abp719/RIOT,watr-li/RIOT,roberthartung/RIOT,mtausig/RIOT,latsku/RIOT,stevenj/RIOT,asanka-code/RIOT,toonst/RIOT,Yonezawa-T2/RIOT,immesys/RiSyn,yogo1212/RIOT,OTAkeys/RIOT,kerneltask/RIOT,stevenj/RIOT,ant9000/RIOT,yogo1212/RIOT,Ell-i/RIOT,plushvoxel/RIOT,lazytech-org/RIOT,OlegHahm/RIOT,dkm/RIOT,rfuentess/RIOT,stevenj/RIOT,kerneltask/RIOT,wentaoshang/RIOT,kb2ma/RIOT,ant9000/RIOT,binarylemon/RIOT,kerneltask/RIOT,asanka-code/RIOT,gebart/RIOT,x3ro/RIOT,jasonatran/RIOT,jbeyerstedt/RIOT-OTA-update,attdona/RIOT,RBartz/RIOT,alignan/RIOT,dkm/RIOT,x3ro/RIOT,d00616/RIOT,khhhh/RIOT,avmelnikoff/RIOT,msolters/RIOT,kerneltask/RIOT,thomaseichinger/RIOT,OTAkeys/RIOT,mziegert/RIOT,malosek/RIOT,mfrey/RIOT,binarylemon/RIOT,kb2ma/RIOT,ks156/RIOT,asanka-code/RIOT,kbumsik/RIOT,gautric/RIOT,Yonezawa-T2/RIOT,kbumsik/RIOT,jbeyerstedt/RIOT-OTA-update,binarylemon/RIOT,attdona/RIOT,MonsterCode8000/RIOT,mziegert/RIOT,RIOT-OS/RIOT,herrfz/RIOT,avmelnikoff/RIOT,yogo1212/RIOT,Yonezawa-T2/RIOT,zhuoshuguo/RIOT,josephnoir/RIOT,d00616/RIOT,lazytech-org/RIOT,jremmert-phytec-iot/RIOT,shady33/RIOT,JensErdmann/RIOT,TobiasFredersdorf/RIOT,FrancescoErmini/RIOT,BytesGalore/RIOT,alignan/RIOT,daniel-k/RIOT,abkam07/RIOT,rakendrathapa/RIOT,Ell-i/RIOT,brettswann/RIOT,tfar/RIOT,msolters/RIOT,josephnoir/RIOT,foss-for-synopsys-dwc-arc-processors/RIOT,MohmadAyman/RIOT,OlegHahm/RIOT,jbeyerstedt/RIOT-OTA-update,biboc/RIOT,A-Paul/RIOT,abkam07/RIOT,backenklee/RIOT,kaleb-himes/RIOT,lebrush/RIOT,l3nko/RIOT,gautric/RIOT,herrfz/RIOT,dhruvvyas90/RIOT,malosek/RIOT,backenklee/RIOT,ks156/RIOT,LudwigOrtmann/RIOT,alignan/RIOT,Josar/RIOT,malosek/RIOT,jasonatran/RIOT,attdona/RIOT,foss-for-synopsys-dwc-arc-processors/RIOT,wentaoshang/RIOT,RBartz/RIOT,malosek/RIOT,wentaoshang/RIOT,basilfx/RIOT,wentaoshang/RIOT,kaleb-himes/RIOT,Ell-i/RIOT,plushvoxel/RIOT,LudwigKnuepfer/RIOT,BytesGalore/RIOT,kYc0o/RIOT,Hyungsin/RIOT-OS,kYc0o/RIOT,haoyangyu/RIOT,yogo1212/RIOT,khhhh/RIOT,rousselk/RIOT,alignan/RIOT,neumodisch/RIOT,shady33/RIOT,ant9000/RIOT,mfrey/RIOT,beurdouche/RIOT,abkam07/RIOT,toonst/RIOT,mfrey/RIOT,zhuoshuguo/RIOT,MohmadAyman/RIOT,backenklee/RIOT,beurdouche/RIOT,josephnoir/RIOT,syin2/RIOT,kb2ma/RIOT,smlng/RIOT,mfrey/RIOT,l3nko/RIOT,asanka-code/RIOT,MonsterCode8000/RIOT,LudwigOrtmann/RIOT,authmillenon/RIOT,kaspar030/RIOT,gautric/RIOT,kYc0o/RIOT,dailab/RIOT,TobiasFredersdorf/RIOT,watr-li/RIOT,haoyangyu/RIOT,basilfx/RIOT,khhhh/RIOT,kYc0o/RIOT,shady33/RIOT,yogo1212/RIOT,rajma996/RIOT,biboc/RIOT,gautric/RIOT,lazytech-org/RIOT,RBartz/RIOT,smlng/RIOT,plushvoxel/RIOT,gebart/RIOT,jbeyerstedt/RIOT-OTA-update,kaspar030/RIOT,beurdouche/RIOT,LudwigKnuepfer/RIOT,rajma996/RIOT,rousselk/RIOT,RIOT-OS/RIOT,aeneby/RIOT,abkam07/RIOT,jfischer-phytec-iot/RIOT,roberthartung/RIOT,watr-li/RIOT,dhruvvyas90/RIOT,immesys/RiSyn,Josar/RIOT,brettswann/RIOT,MohmadAyman/RIOT,syin2/RIOT,haoyangyu/RIOT,Hyungsin/RIOT-OS,mtausig/RIOT,beurdouche/RIOT,basilfx/RIOT,neumodisch/RIOT,A-Paul/RIOT,Yonezawa-T2/RIOT,basilfx/RIOT,jfischer-phytec-iot/RIOT,RubikonAlpha/RIOT,smlng/RIOT,dailab/RIOT,RubikonAlpha/RIOT,immesys/RiSyn,abkam07/RIOT,ks156/RIOT,RBartz/RIOT,adjih/RIOT,gebart/RIOT,dhruvvyas90/RIOT,l3nko/RIOT,dkm/RIOT,rfuentess/RIOT,rfuentess/RIOT,dailab/RIOT,daniel-k/RIOT,adjih/RIOT,jremmert-phytec-iot/RIOT,Hyungsin/RIOT-OS,BytesGalore/RIOT,brettswann/RIOT,dhruvvyas90/RIOT,miri64/RIOT,lebrush/RIOT,roberthartung/RIOT,syin2/RIOT,gebart/RIOT,neumodisch/RIOT,miri64/RIOT,backenklee/RIOT,zhuoshuguo/RIOT,BytesGalore/RIOT,kaleb-himes/RIOT,neumodisch/RIOT,rajma996/RIOT,A-Paul/RIOT,brettswann/RIOT,Yonezawa-T2/RIOT,brettswann/RIOT,jremmert-phytec-iot/RIOT,adjih/RIOT,abp719/RIOT,rousselk/RIOT,kb2ma/RIOT,binarylemon/RIOT,jasonatran/RIOT,dhruvvyas90/RIOT,backenklee/RIOT,kaspar030/RIOT,kYc0o/RIOT,dkm/RIOT,thomaseichinger/RIOT,malosek/RIOT,latsku/RIOT,watr-li/RIOT,rakendrathapa/RIOT,JensErdmann/RIOT,Josar/RIOT,avmelnikoff/RIOT,cladmi/RIOT,foss-for-synopsys-dwc-arc-processors/RIOT,lebrush/RIOT,rakendrathapa/RIOT,RubikonAlpha/RIOT,stevenj/RIOT,MonsterCode8000/RIOT,asanka-code/RIOT,binarylemon/RIOT,toonst/RIOT,attdona/RIOT,RIOT-OS/RIOT,abkam07/RIOT,MonsterCode8000/RIOT,haoyangyu/RIOT,altairpearl/RIOT,biboc/RIOT,daniel-k/RIOT,attdona/RIOT,abp719/RIOT,neiljay/RIOT,RIOT-OS/RIOT,latsku/RIOT,BytesGalore/RIOT,rousselk/RIOT,basilfx/RIOT,d00616/RIOT,RBartz/RIOT,thomaseichinger/RIOT,smlng/RIOT,kaspar030/RIOT,mtausig/RIOT,MonsterCode8000/RIOT,Josar/RIOT,rousselk/RIOT,dkm/RIOT,FrancescoErmini/RIOT,rajma996/RIOT,josephnoir/RIOT,aeneby/RIOT,miri64/RIOT,jfischer-phytec-iot/RIOT,binarylemon/RIOT,latsku/RIOT,OTAkeys/RIOT,smlng/RIOT,MohmadAyman/RIOT,RubikonAlpha/RIOT,zhuoshuguo/RIOT,jremmert-phytec-iot/RIOT,herrfz/RIOT,JensErdmann/RIOT,adrianghc/RIOT,hamilton-mote/RIOT-OS,JensErdmann/RIOT,OlegHahm/RIOT,mtausig/RIOT,kbumsik/RIOT,cladmi/RIOT,abp719/RIOT,cladmi/RIOT,x3ro/RIOT,jfischer-phytec-iot/RIOT,OlegHahm/RIOT,adrianghc/RIOT,toonst/RIOT,LudwigOrtmann/RIOT,alignan/RIOT,syin2/RIOT,neiljay/RIOT,herrfz/RIOT,rfuentess/RIOT,RubikonAlpha/RIOT,neiljay/RIOT,TobiasFredersdorf/RIOT,Yonezawa-T2/RIOT,authmillenon/RIOT,zhuoshuguo/RIOT,FrancescoErmini/RIOT,aeneby/RIOT,A-Paul/RIOT,khhhh/RIOT,LudwigKnuepfer/RIOT,wentaoshang/RIOT,immesys/RiSyn,jremmert-phytec-iot/RIOT,dailab/RIOT,miri64/RIOT,foss-for-synopsys-dwc-arc-processors/RIOT,d00616/RIOT,neumodisch/RIOT,daniel-k/RIOT,tfar/RIOT,authmillenon/RIOT,FrancescoErmini/RIOT,lebrush/RIOT,haoyangyu/RIOT,jfischer-phytec-iot/RIOT,rajma996/RIOT,immesys/RiSyn,avmelnikoff/RIOT,lebrush/RIOT,beurdouche/RIOT,mziegert/RIOT,aeneby/RIOT,zhuoshuguo/RIOT,RBartz/RIOT,d00616/RIOT,FrancescoErmini/RIOT,daniel-k/RIOT,authmillenon/RIOT,d00616/RIOT,brettswann/RIOT,biboc/RIOT,altairpearl/RIOT,haoyangyu/RIOT,daniel-k/RIOT,altairpearl/RIOT,kbumsik/RIOT,neumodisch/RIOT,herrfz/RIOT,rakendrathapa/RIOT,hamilton-mote/RIOT-OS,FrancescoErmini/RIOT,gautric/RIOT,yogo1212/RIOT,lazytech-org/RIOT,thomaseichinger/RIOT