msm: kgsl: Support command batch profiling

This feature allows us to profile the length of completion for
a certain cmdbatch using the RBBM_ALWAYSON_COUNTER. We provide the
userspace with the timer values after the cmdbatch has been
submitted to the ringbuffer, GPU begins execution and finishes
execution on the cmdbatch.

Change-Id: Iacdb6f991084a32a7bf6139eae39067bc1f9b765
Signed-off-by: Shrenuj Bansal <shrenujb@codeaurora.org>