mdss: rotator: fix pm_suspend to no longer release rot sessions

Rotator was releasing all open rotator sessions whenever
pm_suspend was called. This resulted in rotator trying to access
memory that was freed after resume was called. We are now only
cancel all rotator request (rotator work items) on pm_suspend.

Change-Id: Ib63e49213e6fbdec216888e4e7d3fb29defa3903
Signed-off-by: Terence Hampson <thampson@codeaurora.org>