[media] vivid: use consistent colorspace/Y'CbCr Encoding strings

Keep the colorspace and encoding names consistent with what is
used elsewhere (primarily the utilities in v4l-utils.git).

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