[media] dvb core: rename the media controller entities

Prefix all DVB media controller entities with "dvb-" and use dash
instead of underline at the names.

Requested-by: Hans Verkuil <hans.verkuil@cisco.com>

Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>