msm: sde: Add v4l2 rotator driver to enable multi-context usecase

Current application interface of fbdev rotator driver has limited
support on multiple concurrent rotator sessions.  Using v4l2 m2m
framework will enable concurrent multi-session using standard
v4l2 interface.  This will also enable third-party clients to
use rotator service in background mode.

The driver supports same feature set as current fbdev rotator
driver, such as rotation, flip, and scale operation.

CRs-Fixed: 972831
Change-Id: I0bba76f2233c142b5a22451f824df7900ac60afa
Signed-off-by: Alan Kwong <akwong@codeaurora.org>