msm: kgsl: Send a pipeline stat event at GPU start

Send a pipeline stat event whenever the GPU gets powered up
to cause perf counters using countables RB_PS_INVOCATIONS
and HLSQ_CS_INVOCATIONS to start ticking.

Change-Id: Idb9254872ecda59eb4b27410c64ba7b51d0eeb3d
Signed-off-by: Tarun Karra <tkarra@codeaurora.org>