drm/msm/sde: support left/right only partial updates

Add support for partial update regions of interest that fall
entirely on one other side of the display panel. In this case we
want to send the update only to the affected panel.

Change-Id: Idf951da02e1f591a9eaf524d1a8fbce41e150106
Signed-off-by: Lloyd Atkinson <latkinso@codeaurora.org>