msm: kgsl: Add a pwrscale policy to interact with msm_dcvs

This pwrscale policy provides per-core idle information to the
msm_dcvs driver.  It accepts frequency updates from the msm_dcvs
driver and updates the core frequency as needed.

Change-Id: I201cfcb6ceedc19c27f7848781813d9c477f9f83
Signed-off-by: Lucille Sylvester <lsylvest@codeaurora.org>

modified for msm8660 by lolhi