msm: kgsl: Disable unused GPU OPP

GPU HW supports multiple OPP but SW doesn't use all of them always.
SW uses only certain OPP based on requirements or speed-bins.
Because of this reason GPU available_frequency shown by KGSL sysfs
doesn't match with devfreq sysfs.

This change disables OPP which SW doesn't use to make sure GPU
available_frequency displayed by KGSL sysfs and devfreq sysfs
are consistent.

Signed-off-by: Deepak Kumar <dkumar@codeaurora.org>
Change-Id: I9f9ad593e7003949cbc0897e714d2777e782495f