msm: mdss: control when MMSS GDSC gets turned off

RPM has no way to know if they have to disable the MMSS gdsc
during idle power collapse or if its a full suspend.
Setting up the RPM RAM msg to 1 going into idle power collapse
and setting it to 0 while going to full suspend.
All these states mentioned are from a display point of
view.

Crs-Fixed: 1068650
Change-Id: I0ed47e89f6a4dd332ff28e8a1203ae3bfe44e7fa
Signed-off-by: Siddhartha Agrawal <agrawals@codeaurora.org>