drm/mdm/sde: add plane fetch halt

Add vbif transaction halt on a plane that is not used in the next frame.
Multiple planes are associated to a crtc for each frame/commit. These
planes can be reused or not in subsequent commits/frames. Halting the
vbif transactions on the unused plane ensures that there are no spurious
transactions due to this plane.

Change-Id: Ib95625cb7eef3f2777d976f0fc8b7fb855c5c680
Signed-off-by: Harsh Sahu <hsahu@codeaurora.org>