drm/msm/sde: correct VIG GAMUT/IGC opmode address for read

When programing VIG feature blocks, LUT DMA path and AHB path use
different base address of VIG.

LUT DMA is used for writing the VIG features, and AHB is used for
reading the opmode. This change corrects the VIG Gamut/IGC opmode
address for reading.

Change-Id: Ia2dbe66f731383ff988e99814911aa05e6143971
Signed-off-by: Ping Li <pingli@codeaurora.org>