cpu/samd21: Add CPU series specific Kconfig symbols
cpu/samd21: Add CPU series specific Kconfig symbols

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