msm: kgsl: Add init power level sysfs control feature

Add a sysfs element to control kgsl init power level. This sysfs element
allows applications to modify the gpu initial power level
and wake up gpu on lower or higher frequencies.

Change-Id: I28a887a7600c2417d528a348c3554b30a566334f
Signed-off-by: Vladimir Razgulin <vrazguli@codeaurora.org>