drm/msm/sde: make LUTDMA kickoff as blocking for video mode

Currently LUTDMA kickoff is immediately followed by CTL flush,
immaterial of the LUTDMA DONE status. If LUTDMA kickoff happens
too close to the VSYNC, 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.
This issue is applicable only for video-mode as it has to update
on every VSYNC.

Change-Id: I4ebe442045c918c7b4d46fa3f550b4b2c109715d
Signed-off-by: Veera Sundaram Sankaran <veeras@codeaurora.org>