msm: mdss: Ensure MDSS GDSC switched off during FB PM suspend

There are some cases where MDSS GSDC is not turned off after FB
PM suspend ever after clock ref count is 0 as runtime suspend
is not triggered. Ensure that MDSS GDCC is toggled in these
cases.

Change-Id: I33389ad736960b619b32a9bec4b2b157eed4d20b
Signed-off-by: Jayant Shekhar <jshekhar@codeaurora.org>