tests/driver_my9221: fix for loop indexes
tests/driver_my9221: fix for loop indexes

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