cpu/atmega256rfr2: Add Kconfig symbols
cpu/atmega256rfr2: Add Kconfig symbols

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