[media] vivid: don't mention the obsolete sYCC Y'CbCr encoding

This encoding is identical to the 601 encoding. The old duplicate
SYCC define is about to be removed for use in the kernel, so remove
its use in vivid first.

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