cpu/sam0_common: I2C: add support for SAMD20
cpu/sam0_common: I2C: add support for SAMD20

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