drm/msm/sde: Move LUT memeory retention handling to IPC cases

Move LUT memory retention enable/disable handling to CRTC power
event. When IPC suspend, LUT memory retention is enabled. And
when IPC resume, LUT memory retention is disabled. Change fixes
the issue of AD flicker in IPC transition after connect and
disconnect DP.

CRs-Fixed: 2309686
Change-Id: I8215c845cf34fbd216161c01d78d669cfe3fd07b
Signed-off-by: Xu Yang <yangxu@codeaurora.org>