[media] s2255: choose YUYV as the default format, not YUV422P

The planar YUV422P is quite unusual and few if any applications support it.
Instead choose the common YUYV format as the default.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>