drm/msm/sde: add support for vblank callback

Add ability for CRTC to control whether encoder generates
vblank callbacks depending on whether upper layer DRM requests
vblank events.

Change-Id: I5a63afa2765c43d220bfbbedd81d19c3a64de7d7
Signed-off-by: Abhijit Kulkarni <kabhijit@codeaurora.org>
9 files changed