msm: kgsl: Remove event worker

Scheduling issues were occurring with the GPU event worker after
b7be8076 (msm: kgsl: Unbind the kgsl-event workqueue) was merged.
In certain conditions, it seems that the kgsl-event workqueue
was conflicting with the KGSL worker and slowing it down.

It turns out that everywhere we schedule the event worker
and the dispatcher worker at the same time.  Since the worker
is singlethread, the event worker and the dispatcher run
synchronously anyway, so it makes sense to run the event processor
from within the dispatcher and save the extra schedule.

Change-Id: Ic0dedbad67eb04d41afb6add4477f146dfff9784
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>