cpu/cc2538/spi: Fix compiler warning of possible uninitialized variable
cpu/cc2538/spi: Fix compiler warning of possible uninitialized variable

LudwigOrtmann/RIOT,A-Paul/RIOT,jfischer-phytec-iot/RIOT,immesys/RiSyn,alignan/RIOT,dailab/RIOT,wentaoshang/RIOT,Ell-i/RIOT,OTAkeys/RIOT,immesys/RiSyn,zhuoshuguo/RIOT,plushvoxel/RIOT,dailab/RIOT,neiljay/RIOT,smlng/RIOT,Hyungsin/RIOT-OS,plushvoxel/RIOT,roberthartung/RIOT,avmelnikoff/RIOT,gebart/RIOT,adrianghc/RIOT,tfar/RIOT,backenklee/RIOT,zhuoshuguo/RIOT,ks156/RIOT,d00616/RIOT,wentaoshang/RIOT,biboc/RIOT,hamilton-mote/RIOT-OS,adjih/RIOT,OTAkeys/RIOT,kaspar030/RIOT,A-Paul/RIOT,LudwigKnuepfer/RIOT,mtausig/RIOT,Hyungsin/RIOT-OS,basilfx/RIOT,rousselk/RIOT,cladmi/RIOT,dkm/RIOT,syin2/RIOT,thomaseichinger/RIOT,wentaoshang/RIOT,plushvoxel/RIOT,katezilla/RIOT,jasonatran/RIOT,kaspar030/RIOT,ant9000/RIOT,rajma996/RIOT,brettswann/RIOT,jremmert-phytec-iot/RIOT,ant9000/RIOT,brettswann/RIOT,neumodisch/RIOT,tfar/RIOT,TobiasFredersdorf/RIOT,jfischer-phytec-iot/RIOT,x3ro/RIOT,Ell-i/RIOT,ks156/RIOT,cladmi/RIOT,malosek/RIOT,kerneltask/RIOT,kb2ma/RIOT,A-Paul/RIOT,authmillenon/RIOT,altairpearl/RIOT,adrianghc/RIOT,kaleb-himes/RIOT,toonst/RIOT,immesys/RiSyn,attdona/RIOT,jfischer-phytec-iot/RIOT,adjih/RIOT,RIOT-OS/RIOT,attdona/RIOT,TobiasFredersdorf/RIOT,jasonatran/RIOT,Josar/RIOT,dailab/RIOT,gautric/RIOT,Josar/RIOT,brettswann/RIOT,neumodisch/RIOT,roberthartung/RIOT,ks156/RIOT,yogo1212/RIOT,altairpearl/RIOT,LudwigOrtmann/RIOT,syin2/RIOT,LudwigOrtmann/RIOT,foss-for-synopsys-dwc-arc-processors/RIOT,zhuoshuguo/RIOT,LudwigKnuepfer/RIOT,rajma996/RIOT,OTAkeys/RIOT,gebart/RIOT,backenklee/RIOT,kerneltask/RIOT,alignan/RIOT,altairpearl/RIOT,josephnoir/RIOT,hamilton-mote/RIOT-OS,d00616/RIOT,attdona/RIOT,plushvoxel/RIOT,neumodisch/RIOT,gebart/RIOT,wentaoshang/RIOT,TobiasFredersdorf/RIOT,kbumsik/RIOT,mtausig/RIOT,thomaseichinger/RIOT,d00616/RIOT,kaleb-himes/RIOT,beurdouche/RIOT,Hyungsin/RIOT-OS,RIOT-OS/RIOT,backenklee/RIOT,altairpearl/RIOT,d00616/RIOT,smlng/RIOT,yogo1212/RIOT,d00616/RIOT,LudwigOrtmann/RIOT,TobiasFredersdorf/RIOT,katezilla/RIOT,adrianghc/RIOT,cladmi/RIOT,kerneltask/RIOT,biboc/RIOT,Josar/RIOT,rousselk/RIOT,jasonatran/RIOT,hamilton-mote/RIOT-OS,kb2ma/RIOT,wentaoshang/RIOT,backenklee/RIOT,yogo1212/RIOT,x3ro/RIOT,kaspar030/RIOT,gebart/RIOT,kbumsik/RIOT,alignan/RIOT,mfrey/RIOT,mtausig/RIOT,rfuentess/RIOT,beurdouche/RIOT,biboc/RIOT,ant9000/RIOT,BytesGalore/RIOT,jremmert-phytec-iot/RIOT,dkm/RIOT,immesys/RiSyn,foss-for-synopsys-dwc-arc-processors/RIOT,basilfx/RIOT,alignan/RIOT,mtausig/RIOT,toonst/RIOT,authmillenon/RIOT,rajma996/RIOT,x3ro/RIOT,malosek/RIOT,dkm/RIOT,mfrey/RIOT,kYc0o/RIOT,kaleb-himes/RIOT,avmelnikoff/RIOT,kYc0o/RIOT,roberthartung/RIOT,immesys/RiSyn,Josar/RIOT,rajma996/RIOT,x3ro/RIOT,basilfx/RIOT,josephnoir/RIOT,kb2ma/RIOT,OlegHahm/RIOT,jasonatran/RIOT,OlegHahm/RIOT,dailab/RIOT,cladmi/RIOT,basilfx/RIOT,kerneltask/RIOT,dkm/RIOT,neiljay/RIOT,jremmert-phytec-iot/RIOT,Ell-i/RIOT,toonst/RIOT,neumodisch/RIOT,beurdouche/RIOT,OTAkeys/RIOT,neiljay/RIOT,A-Paul/RIOT,syin2/RIOT,thomaseichinger/RIOT,RIOT-OS/RIOT,hamilton-mote/RIOT-OS,zhuoshuguo/RIOT,dkm/RIOT,jasonatran/RIOT,BytesGalore/RIOT,gebart/RIOT,ant9000/RIOT,toonst/RIOT,miri64/RIOT,aeneby/RIOT,josephnoir/RIOT,A-Paul/RIOT,OlegHahm/RIOT,jbeyerstedt/RIOT-OTA-update,alignan/RIOT,jbeyerstedt/RIOT-OTA-update,ant9000/RIOT,katezilla/RIOT,beurdouche/RIOT,rousselk/RIOT,roberthartung/RIOT,syin2/RIOT,immesys/RiSyn,yogo1212/RIOT,biboc/RIOT,syin2/RIOT,Ell-i/RIOT,OTAkeys/RIOT,malosek/RIOT,brettswann/RIOT,rfuentess/RIOT,BytesGalore/RIOT,gautric/RIOT,foss-for-synopsys-dwc-arc-processors/RIOT,authmillenon/RIOT,malosek/RIOT,BytesGalore/RIOT,Ell-i/RIOT,RIOT-OS/RIOT,aeneby/RIOT,malosek/RIOT,altairpearl/RIOT,aeneby/RIOT,zhuoshuguo/RIOT,neiljay/RIOT,smlng/RIOT,mfrey/RIOT,gautric/RIOT,beurdouche/RIOT,rfuentess/RIOT,x3ro/RIOT,ks156/RIOT,jfischer-phytec-iot/RIOT,kYc0o/RIOT,LudwigKnuepfer/RIOT,jbeyerstedt/RIOT-OTA-update,thomaseichinger/RIOT,authmillenon/RIOT,kb2ma/RIOT,kaspar030/RIOT,smlng/RIOT,smlng/RIOT,katezilla/RIOT,jremmert-phytec-iot/RIOT,kbumsik/RIOT,avmelnikoff/RIOT,tfar/RIOT,ks156/RIOT,authmillenon/RIOT,gautric/RIOT,rfuentess/RIOT,lazytech-org/RIOT,lazytech-org/RIOT,TobiasFredersdorf/RIOT,adrianghc/RIOT,toonst/RIOT,neiljay/RIOT,zhuoshuguo/RIOT,wentaoshang/RIOT,brettswann/RIOT,attdona/RIOT,josephnoir/RIOT,BytesGalore/RIOT,LudwigOrtmann/RIOT,Josar/RIOT,adjih/RIOT,RIOT-OS/RIOT,kYc0o/RIOT,attdona/RIOT,mtausig/RIOT,avmelnikoff/RIOT,LudwigOrtmann/RIOT,kb2ma/RIOT,roberthartung/RIOT,kYc0o/RIOT,josephnoir/RIOT,aeneby/RIOT,kaspar030/RIOT,rajma996/RIOT,adjih/RIOT,neumodisch/RIOT,kaleb-himes/RIOT,rousselk/RIOT,jbeyerstedt/RIOT-OTA-update,avmelnikoff/RIOT,rfuentess/RIOT,miri64/RIOT,mfrey/RIOT,miri64/RIOT,altairpearl/RIOT,OlegHahm/RIOT,mfrey/RIOT,miri64/RIOT,foss-for-synopsys-dwc-arc-processors/RIOT,adrianghc/RIOT,d00616/RIOT,LudwigKnuepfer/RIOT,rousselk/RIOT,thomaseichinger/RIOT,tfar/RIOT,dailab/RIOT,foss-for-synopsys-dwc-arc-processors/RIOT,hamilton-mote/RIOT-OS,jremmert-phytec-iot/RIOT,adjih/RIOT,LudwigKnuepfer/RIOT,aeneby/RIOT,gautric/RIOT,kerneltask/RIOT,yogo1212/RIOT,malosek/RIOT,plushvoxel/RIOT,kbumsik/RIOT,rajma996/RIOT,kbumsik/RIOT,miri64/RIOT,attdona/RIOT,cladmi/RIOT,Hyungsin/RIOT-OS,katezilla/RIOT,biboc/RIOT,tfar/RIOT,backenklee/RIOT,lazytech-org/RIOT,lazytech-org/RIOT,rousselk/RIOT,jbeyerstedt/RIOT-OTA-update,OlegHahm/RIOT,neumodisch/RIOT,yogo1212/RIOT,Hyungsin/RIOT-OS,jremmert-phytec-iot/RIOT,jfischer-phytec-iot/RIOT,kaleb-himes/RIOT,authmillenon/RIOT,brettswann/RIOT,lazytech-org/RIOT,basilfx/RIOT