media: allegro: nal-hevc: implement generator for vui

The NAL unit generator for HEVC does not support the generation of vui
parameters. Implement it to allow drivers to set the vui parameters in
the coded video stream.

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>