msm: mdss : Display always on feature support

Currently, the only power state transition supported is ON<->OFF.
Added support in the display driver to handle the intermediate
low power state (LP1 corresponding to DOZE/DOZE_SUSPEND).

Change-Id: I814400dfb6f7336a2acda0dc42b8c626b435c1e0
Signed-off-by: Sravanthi Kollukuduru <skolluku@codeaurora.org>