mdss: msm: Add support for gamut map enable

Non-uniform mapping mode is configurable parameter exposed by MDP.
Driver should provide the option to gamut clients to configure the
mapping. Change updates the interface to expose the parameter and
programs the gamut registers based on user setting.

Change-Id: I71e7e0f7443da7856b0d03e6b2799f9380274893
Signed-off-by: Gopikrishnaiah Anandan <agopik@codeaurora.org>