msm: kgsl: Set gmu fault inside gmu_snapshot

The two always happen together. So set the gmu_fault
inside the gmu_snapshot function. Also, if we have
already recorded a gmu fault, then do not send nmi
or try to snapshot a gmu which is already in nmi.

Change-Id: I403a9c2c3cb7a1330a7931c41a23b4b4a2b66998
Signed-off-by: Harshdeep Dhatt <hdhatt@codeaurora.org>