msm: kgsl: Add a6xx_hwsched_snapshot function

Since GMU tells us the exact submission that faulted via
the context bad hfi, look up the command object corresponding
to the submission and mark it for snapshot purposes. Create the
top level gpudev snapshot function for hw scheduling which first
snapshots the faulted command object and then calls into the
generic gmu snapshot function.

Change-Id: I5c5300b7b147dfcf0c009b44376ba0c6e1f8e25b
Signed-off-by: Harshdeep Dhatt <hdhatt@codeaurora.org>