msm: sde: Add interface to support sde v4l2 rotator

Current fbdev rotator interface lacks support for mult-context
use cases.  This new interface adopts V4L2 M2M framework to
support multiple concurrent sessions/contexts efficiently.

CRs-Fixed: 972831
Change-Id: I89593a57ba44e91c95d73154a7830539e5aab6e3
Signed-off-by: Alan Kwong <akwong@codeaurora.org>