msm: kgsl: Ensure that thermal power level restrictions are enforced

Add checks to make sure thermal power level restrictions are
enforced and power level is always within thermal min and max
limit. Currently, thermal limits are breached in cases where
GPU min_pwrlevel and max_pwrlevel sysfs entries are updated by
performance daemon to maintain performance and thermal mitigation
kicks in at same time.

Change-Id: Id3f0c2d878588633398d20d43223b26ec292b98e
Signed-off-by: Deepak Kumar <dkumar@codeaurora.org>