boards/nrf52: remove periph_gpio feature
boards/nrf52: remove periph_gpio feature

It is now provided at cpu level in cpu/nrf5x_common

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