msm: mdss: mdp: add input event handler

Attach an input event handler from mdp driver. In static screen cases
with command mode panel, mdp driver will wake up from idle state up on
receiving event from input driver. This will reduce latency during frame
kick off.

Change-Id: I60676915fea6f95a4aad5f49e09123d1a43f70cc
Signed-off-by: Vinu Deokaran <vinud@codeaurora.org>