adreno_tz: Check that partner_gpu_profile is not NULL before using it

The governor events are scheduled work tasks so it is possible for the
TZ to be shut down after the event is scheduled but before it is run.
If that happens partner_gpu_profile might be NULL so check it to be
safe before executing any of the event request.

Change-Id: Ic0dedbad428198054ec46d30fbebba03edb5d5d7
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>