msm: kgsl: Run the event group after the context is invalidated

After a context is invalidated force the context event group to run
to process all the pending events.  If the context is invalidated
but not yet destroyed there might be dangling fence or freememontimestamp
events that will go unrun.

CRs-Fixed: 710362
Change-Id: Ic0dedbad5976236d811b50af87fbff038f639dc0
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>