msm: mdss: Optimize Gamut Mapping programming sequence

Gamut mapping feature has a huge size 3D LUT table, which consumes
a lot of time to program. This patch optimizes the programming of
the 3D LUT to reduce about half of the register writes.

Change-Id: I4a9fcee6c1cd70d9c04426c394e480c11a6f4648
Signed-off-by: Ping Li <pingli@codeaurora.org>