drm/msm/sde: ensure LUTDMA is complete when auto-refresh enable

Currently LUTDMA kickoff is immediately followed by CTL flush,
immaterial of the LUTDMA DONE status in command mode. If LUTDMA
kickoff happens too close to the read_ptr in auto-refresh case, it might
cause a race condition between LUTDMA & CTL flush, due to a HW issue.
Serialize LUTDMA & CTL flush by making the LUTDMA kickoff as blocking
to avoid the race condition in auto-refresh case similar to video mode.

Change-Id: I4f4ae90a2c4f1bc8a0686d8fd4f8aa439123c531
Signed-off-by: Raviteja Tamatam <travitej@codeaurora.org>