msm: kgsl: Move gmu_fault from snapshot structure

Add gmu_fault member to kgsl device structure and remove it
from snapshot, a6xx gmu and rgmu structures. This helps in
removing snapshot function from the gmu core ops in the next
patch.

Change-Id: I5f2aba879ebf0330ef2c73d1d2fa4a2032bb6c9b
Signed-off-by: Harshdeep Dhatt <hdhatt@codeaurora.org>