media: v4l2-ctrls: Add RGB color effects control

Add V4L2_COLORFX_SET_RGB color effects control, V4L2_CID_COLORFX_RGB
for RGB color setting.

with two mirror changes:
- change 0xFFFFFF to 0xffffff
- fix comments 2^24 to 2^24 - 1

[hverkuil: dropped spaces around + with V4L2_CID_BASE for consistency]

Signed-off-by: Dillon Min <dillon.minfei@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>