[media] v4l2-mc: cleanup a warning

A previous patch removing dtv_demod needed to be rebased,
but the hunk removing the data was not merged by mistake.

Fixes: 840f5b05 ('media: au0828 disable tuner to demod link in au0828_media_device_register()']

Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>