drm/msm: support partial update of dsi panel output

Add support in the DSI DRM driver for partial update. A user's
region of interest request is used to send DCS col/page commands
to the DSI panel to update only a given region on the panel.

Change-Id: I42a462076537131a6f8806bc011af0b80fdfa64e
Signed-off-by: Lloyd Atkinson <latkinso@codeaurora.org>