FROMGIT: media: v4l2-ctrl: Add decoder conceal color control

Add decoder v4l2 control to set conceal color.

Signed-off-by: Stanimir Varbanov <stanimir.varbanov@linaro.org>
Reviewed-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
(cherry picked from commit b52051a4
 git://linuxtv.org/media_tree.git master)
Bug: 183579772
Link: https://lkml.org/lkml/2021/2/9/252



Change-Id: I49cac2c1b27cdac72f7dbbb602d2387fd006ff98
Signed-off-by: Dikshita Agarwal <dikshita@codeaurora.org>