drm/msm/sde: Update LUT DMA offset for future expansion

The LUT DMA register offsets has been updated from SDM845 to SDM855,
this change changes these offsets from macros to static variables,
so that these can be set correctly according to the LUT DMA version.

Change-Id: I0f9ef388faa08240e7a2ee80f445ee6309baf906
Signed-off-by: Ping Li <pingli@codeaurora.org>