msm: kgsl: Store cmdbatch execution times from submit to retire

Store the time delta from cmdbatch submit to retire and dump
it in the event of fence timeout on fences that we own. This
piece of information helps debug fence timeout issues.

Change-Id: If4c89b70234998627df73f1cf133d8f7634bc937
Signed-off-by: Harshdeep Dhatt <hdhatt@codeaurora.org>