sys/saul_reg: Fix saul_reg_rm for first element
sys/saul_reg: Fix saul_reg_rm for first element

OTAkeys/RIOT,ant9000/RIOT,rfuentess/RIOT,lazytech-org/RIOT,kYc0o/RIOT,basilfx/RIOT,josephnoir/RIOT,yogo1212/RIOT,A-Paul/RIOT,rfuentess/RIOT,rfuentess/RIOT,kbumsik/RIOT,A-Paul/RIOT,LudwigOrtmann/RIOT,RIOT-OS/RIOT,kaspar030/RIOT,yogo1212/RIOT,RIOT-OS/RIOT,aeneby/RIOT,RIOT-OS/RIOT,LudwigKnuepfer/RIOT,x3ro/RIOT,mtausig/RIOT,josephnoir/RIOT,yogo1212/RIOT,LudwigOrtmann/RIOT,neiljay/RIOT,aeneby/RIOT,BytesGalore/RIOT,basilfx/RIOT,LudwigOrtmann/RIOT,LudwigKnuepfer/RIOT,LudwigOrtmann/RIOT,josephnoir/RIOT,cladmi/RIOT,LudwigOrtmann/RIOT,smlng/RIOT,miri64/RIOT,smlng/RIOT,ant9000/RIOT,avmelnikoff/RIOT,A-Paul/RIOT,authmillenon/RIOT,aeneby/RIOT,cladmi/RIOT,neiljay/RIOT,lazytech-org/RIOT,gebart/RIOT,kYc0o/RIOT,kYc0o/RIOT,BytesGalore/RIOT,toonst/RIOT,cladmi/RIOT,mtausig/RIOT,mfrey/RIOT,neiljay/RIOT,kaspar030/RIOT,cladmi/RIOT,avmelnikoff/RIOT,OTAkeys/RIOT,BytesGalore/RIOT,OlegHahm/RIOT,josephnoir/RIOT,lazytech-org/RIOT,kaspar030/RIOT,kYc0o/RIOT,BytesGalore/RIOT,yogo1212/RIOT,kYc0o/RIOT,LudwigKnuepfer/RIOT,biboc/RIOT,yogo1212/RIOT,A-Paul/RIOT,miri64/RIOT,mfrey/RIOT,ant9000/RIOT,basilfx/RIOT,jasonatran/RIOT,toonst/RIOT,jasonatran/RIOT,OlegHahm/RIOT,ant9000/RIOT,authmillenon/RIOT,avmelnikoff/RIOT,authmillenon/RIOT,neiljay/RIOT,basilfx/RIOT,miri64/RIOT,aeneby/RIOT,authmillenon/RIOT,x3ro/RIOT,OlegHahm/RIOT,OTAkeys/RIOT,toonst/RIOT,kbumsik/RIOT,josephnoir/RIOT,x3ro/RIOT,biboc/RIOT,OTAkeys/RIOT,smlng/RIOT,LudwigOrtmann/RIOT,authmillenon/RIOT,smlng/RIOT,x3ro/RIOT,toonst/RIOT,OTAkeys/RIOT,rfuentess/RIOT,mfrey/RIOT,rfuentess/RIOT,kbumsik/RIOT,toonst/RIOT,mfrey/RIOT,cladmi/RIOT,jasonatran/RIOT,lazytech-org/RIOT,lazytech-org/RIOT,OlegHahm/RIOT,kaspar030/RIOT,basilfx/RIOT,miri64/RIOT,ant9000/RIOT,gebart/RIOT,jasonatran/RIOT,gebart/RIOT,yogo1212/RIOT,neiljay/RIOT,LudwigKnuepfer/RIOT,avmelnikoff/RIOT,RIOT-OS/RIOT,mfrey/RIOT,jasonatran/RIOT,biboc/RIOT,aeneby/RIOT,kbumsik/RIOT,kbumsik/RIOT,kaspar030/RIOT,biboc/RIOT,gebart/RIOT,authmillenon/RIOT,gebart/RIOT,smlng/RIOT,mtausig/RIOT,RIOT-OS/RIOT,avmelnikoff/RIOT,mtausig/RIOT,LudwigKnuepfer/RIOT,mtausig/RIOT,A-Paul/RIOT,x3ro/RIOT,BytesGalore/RIOT,OlegHahm/RIOT,biboc/RIOT,miri64/RIOT