The vui parameters are optional. However, the vui data allows to specify
the color space of the encoded video. Write the vui parameters to make
sure that decoders are able to pick up the correct color space.

Also implement the necessary lookup functions to convert the values from
the V4L2 controls to the values specified in the hevc standard.
Signed-off-by: Michael Tretter <m.tretter@pengutronix.de>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>