drivers: Added doc group drivers_multimedia
drivers: Added doc group drivers_multimedia

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