msm: kgsl: schedule dispatcher after canceling a fence wait

If we are cancelling an async wait on a fence, it is likely that
the context is sitting on the dispatcher queue.  Schedule so that
the dispatcher can remove it from the queue and release its
reference count.

Change-Id: I0517f7d6ad37ed2081f477c867508b659caeccb4
Signed-off-by: Jeremy Gebben <jgebben@codeaurora.org>