msm: kgsl: Add a framework to track timing of power events

Allow histories of events of interest to power control
to be tracked.  Set up separate indexed arrays of each
type of desired event.  Power states and frequency changes
are two examples of tracked events.

Change-Id: I7953b9a34f797591e559a84cfd148307a4e9a4a5
Signed-off-by: Lucille Sylvester <lsylvest@codeaurora.org>