[media] vivid-tpg: add tpg_log_status()

Add a log_status function to the test pattern generator and use that
in vivid. This simplifies debugging complex colorspace problems.

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