Makefile.include: remove useless assignment of none to BOARD
Makefile.include: remove useless assignment of none to BOARD

ant9000/RIOT,kYc0o/RIOT,kaspar030/RIOT,OTAkeys/RIOT,authmillenon/RIOT,kaspar030/RIOT,jasonatran/RIOT,authmillenon/RIOT,kaspar030/RIOT,RIOT-OS/RIOT,basilfx/RIOT,OlegHahm/RIOT,miri64/RIOT,miri64/RIOT,authmillenon/RIOT,RIOT-OS/RIOT,ant9000/RIOT,miri64/RIOT,RIOT-OS/RIOT,basilfx/RIOT,RIOT-OS/RIOT,jasonatran/RIOT,ant9000/RIOT,ant9000/RIOT,kYc0o/RIOT,OlegHahm/RIOT,basilfx/RIOT,OlegHahm/RIOT,OTAkeys/RIOT,RIOT-OS/RIOT,OTAkeys/RIOT,kYc0o/RIOT,basilfx/RIOT,OlegHahm/RIOT,kYc0o/RIOT,authmillenon/RIOT,ant9000/RIOT,kaspar030/RIOT,jasonatran/RIOT,jasonatran/RIOT,authmillenon/RIOT,OTAkeys/RIOT,jasonatran/RIOT,kYc0o/RIOT,OTAkeys/RIOT,basilfx/RIOT,OlegHahm/RIOT,miri64/RIOT,authmillenon/RIOT,kaspar030/RIOT,miri64/RIOT