msm: kgsl: Log retired timestamps on device wake

Knowing the retired timestamp on wake-up is useful to debug hangs that
are caused due to clock instability. When we request for clock ON, the
clock may/may-not be turned ON, but we go ahead assuming it is ON. This
can be caught by printing the timestamp on wake. The timestamp we print,
can be compared against the timestamp in postmortem dump (assuming a
hang happens).

If there is a difference, we can say that GPU has run for sometime after
wake. So, we needn't suspect clocks.

If there is no difference, we can say that GPU has hung immediately after
wake. So, we can positively suspect the clocks.

Change-Id: Iedf49977adbb0e61a9b71bbe23acc81f2a75162d
Signed-off-by: Ranjhith Kalisamy <ranjhith@codeaurora.org>