drm/msm/sde: add plane restore for idle pc restore

If a plane without state updated was power collapsed,
it will not be scheduled for atomic update by framework
and not be able to restore hardware state on next commit.
To help restore hardware state of these planes, add a
new plane callback for power restore in crtc flush such
that all attached planes can check if hardware state
needed to be restored prior to flush.

Change-Id: If0ab50c12188eb1bfb937c955918dfd9280a95f2
Signed-off-by: Alan Kwong <akwong@codeaurora.org>