drivers/periph_i2c: fix build issue with return code type
drivers/periph_i2c: fix build issue with return code type

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