disp: msm: Use the new notifier function instead of msm_drm_notifier

Since other driver module could not use msm_drm function,
then the notify function was moved to drm_panel. So used
the new drm_panel notify API instead of the old one.

Change-Id: I053992d74125807ccbf8991e3ac771dfc3eef732
Signed-off-by: Yuan Zhao <yzhao@codeaurora.org>