msm: kgsl: Add GPU snapshot support

Add support for snapshotting the state of the GPU in a binary format. The
snapshot can be pulled from sysfs and parsed off-target.  The advantage is
that far more information can be encapsulated in a snapshot then can be
printed on the console during a hang.  Snapshots are automatically created
during a hang, or can be manually triggered by writing 'trigger'
in /sys/class/kgsl/kgsl-<n>/snapshot where n is either the 2D or 3D device.
Snapshot data can be pulled from 'dump' in the same directory.

Change-Id: Ic0dedbad1c8473b3b109582b95a8771b0d341f05
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>