msm: kgsl: Disallow L2PC during wake up from SLUMBER

Add a PM QOS request to disallow L2PC during wake up
from SLUMBER state. This is required to improve queue
to submit time for first set of GPU commands which results
in GPU wake up.

Change-Id: Iad1a6dfdf9e1fe034eef4fae526138d724bdd3eb
Signed-off-by: Gaurav Sonwani <gsonwani@codeaurora.org>