msm: kgsl: Use fault context to retrieve process information

Instead of looking up the process by pagetable base and
name, use the fault context to extract the pid and other
process specific information. This works for both the
per-process and global pagetable configurations and also
reduces some locking. This also reports the correct
pid and task name in the global pagetable configuration.

CRs-Fixed: 971753
Change-Id: I9c869527c3d1b2606f3d12234163935d6f5e43a9
Signed-off-by: Sushmita Susheelendra <ssusheel@codeaurora.org>