msm: kgsl: Pass event group to callback and remove wait parameter

Pass event group to the evnt callback function instead of the context.
We have ringbuffer events that do not have a context and hence it
makes more sense to pass the event group to the callback to handle
ringbuffer events which do not have a context.

Secondly, do not use a parameter when waiting for ringbuffer timestamp
since using this parameter will require synchronization between the
event and the thread waiting for the event. The parameter can only be
destroyed when the event is complete and the wait thread has
exited. This synchronization adds code complexity which can be
avoided by not using the parameter and simply checking changing the
wait condition to see if the event is present on the event list.

Change-Id: I65db1971b1c29b441003be629f89753b1d69c9d0
CRs-Fixed: 717952
Signed-off-by: Shubhraprakash Das <sadas@codeaurora.org>