media: vicodec: move the GREY format to the end of the list

With the GREY format at the beginning, the default format selected
by vicodec would be GREY instead of YUV420. That didn't make sense,
so move it to the end of the list.

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