disp: msm: add notifier driver

Add notifier driver and enable compilation. Notifier
holds a call to scheduler that is required whenever there
is a change in refresh rate. It will pass the max refresh
rate of all active displays to scheduler.

Change-Id: Id4328e9421e7c8be003067972dc0d3e74ad42c4b
Signed-off-by: Samantha Tran <samtran@codeaurora.org>