cpu/efm32: deduplicate cpu_efm32 group definition
cpu/efm32: deduplicate cpu_efm32 group definition

authmillenon/RIOT,x3ro/RIOT,mtausig/RIOT,cladmi/RIOT,smlng/RIOT,toonst/RIOT,OlegHahm/RIOT,cladmi/RIOT,RIOT-OS/RIOT,yogo1212/RIOT,OlegHahm/RIOT,x3ro/RIOT,smlng/RIOT,ant9000/RIOT,kYc0o/RIOT,josephnoir/RIOT,toonst/RIOT,x3ro/RIOT,aeneby/RIOT,ant9000/RIOT,OlegHahm/RIOT,aeneby/RIOT,smlng/RIOT,RIOT-OS/RIOT,rfuentess/RIOT,cladmi/RIOT,josephnoir/RIOT,kaspar030/RIOT,ant9000/RIOT,josephnoir/RIOT,jasonatran/RIOT,kaspar030/RIOT,kaspar030/RIOT,yogo1212/RIOT,authmillenon/RIOT,kaspar030/RIOT,yogo1212/RIOT,yogo1212/RIOT,cladmi/RIOT,kYc0o/RIOT,rfuentess/RIOT,ant9000/RIOT,authmillenon/RIOT,x3ro/RIOT,RIOT-OS/RIOT,smlng/RIOT,kYc0o/RIOT,miri64/RIOT,aeneby/RIOT,OTAkeys/RIOT,rfuentess/RIOT,RIOT-OS/RIOT,miri64/RIOT,mtausig/RIOT,jasonatran/RIOT,kYc0o/RIOT,basilfx/RIOT,yogo1212/RIOT,authmillenon/RIOT,cladmi/RIOT,miri64/RIOT,basilfx/RIOT,smlng/RIOT,OlegHahm/RIOT,OTAkeys/RIOT,aeneby/RIOT,josephnoir/RIOT,mtausig/RIOT,jasonatran/RIOT,aeneby/RIOT,yogo1212/RIOT,jasonatran/RIOT,miri64/RIOT,ant9000/RIOT,OTAkeys/RIOT,rfuentess/RIOT,authmillenon/RIOT,toonst/RIOT,authmillenon/RIOT,toonst/RIOT,rfuentess/RIOT,basilfx/RIOT,mtausig/RIOT,x3ro/RIOT,mtausig/RIOT,miri64/RIOT,RIOT-OS/RIOT,jasonatran/RIOT,basilfx/RIOT,kYc0o/RIOT,basilfx/RIOT,toonst/RIOT,kaspar030/RIOT,OTAkeys/RIOT,josephnoir/RIOT,OlegHahm/RIOT,OTAkeys/RIOT