media: vicodec: always return a valid format.

Rather than returning width/height values of 0, just default to
a format. Formats in V4L2 are always supposed to be valid, there
is no concept of an invalid format.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>