media: v4l2: remove VBI output pad

The signal there is the same as the video output (well,
except for sliced VBI, but let's simplify the model and ignore
it, at least for now - as it is routed together with raw
VBI).

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