msm: kgsl: protect syncpoint events with a reference count

Replace the event spinlock with krefs to avoid the possiblity
of calling a sleeping function while holding the spinlock and
to generally make the whole cmdbatch cancel loop a lot more
stable.

Change-Id: I08ba54fa4c5a11c05e3503dfc6a4ee040733e5a6
Signed-off-by: Jeff Boody <jboody@codeaurora.org>
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>