msm: kgsl: Add facility to BUG_ON for a gpu fault

Few gpu faults need system level information like voltages,
interface clock etc. This information can't be extracted
through the snapshot dump. Add a facility to force panic
on gpu fault, which will help to extract additional
information from the ramdumps.

To trigger BUG_ON for a gpu fault:
echo 1  > /sys/class/kgsl/kgsl-3d0/snapshot/force_panic

Change-Id: I020b5518fcaedd4fecc572b580a989bf117f6ceb
Signed-off-by: Hareesh Gundu <hareeshg@codeaurora.org>