qseecom: Fix failure to go into suspend

When the device tries to go into suspend the freezer process
fails to put the  blocked threads into sleep.
Hence device is failing to go into suspend as the blocked threads
are woken up by suspend signal (and any signal in general).
Replacing wait_event_interruptable() with wait_event_freezable()
allows the freezer process to freeze the blocked threads,
thereby, allowing the device to proceed with going into suspend.

Change-Id: I3830f056050828cee05c1ff404baaed0318e87c9
Signed-off-by: Mona Hossain <mhossain@codeaurora.org>