msm: kgsl: Make use of performance counter for A2xx.

Add new performance counter for a2xx to track number
of ALU instructions executed. This will help fault tolerance
detection logic to get more accurate data about the GPU.

Change-Id: I4a1afcfa12fd55a8ca1c4827f1fa7ee8e322e9c5
Signed-off-by: Rajesh Kemisetti <rajeshk@codeaurora.org>