boards/nucleo-l476rg: use common rtt configuration
boards/nucleo-l476rg: use common rtt configuration

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