msm_fb: Handle flags for updating AR GC lookup table (LUT)

In current implementation of  area reduced gamma correction (AR-GC)
LUT configuration,flags for read/write AR-GC LUT and enable/disable
AR-GC LUT functionality are not handled even though the IOCTL accepts
these flags as part of arguments. So in current implementation by
default updates the AR-GC LUT which may not be expected always.

So, handle flags for read/write AR-GC LUT and enable/disable updating
area reduced gamma correction (AR GC) functionality

Change-Id: Idd19dd86ec2b8a4b6f22674e522b2f7e06fb63fc
Signed-off-by: Pravin Tamkhane <pravint@codeaurora.org>