drm/msm: Add support for PA vLut feature

Picture adjustment block supports vLut block which can enhance the
contrast of the pixels. Change adds support to expose the feature to
user-space and program the vLut registers for the display.

Change-Id: I9822f9711b9048c5db8c313204a6ba64e013f8a9
Signed-off-by: Gopikrishnaiah Anandan <agopik@codeaurora.org>