disp: msm: sde: cache vbif QoS parameters

Cache vbif QoS parameters to avoid unnecessary reprogramming
of plane vbif registers. This will reduce frame time and
frame drop count.

Change-Id: I20ed97bbac54fa9b11a8784d7a4004f1ccc00632
Signed-off-by: Amine Najahi <anajahi@codeaurora.org>
Signed-off-by: Samantha Tran <samtran@codeaurora.org>