The format of the sink pad should be a bayer mbus format.

This fixes a kernel NULL pointer dereference error that was caused when
the stream starts because the configured format was not found in the
pixelmap table.
Reported-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Helen Koike <helen.koike@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>