msm: kgsl: Add GPU Cx ipeak client support on SDM660

To handle Cx peak current limit on SDM660, GPU needs
to call Cx ipeak driver APIs when it switches between
threshold points.

Cx ipeak driver will throttle cDSP frequency if all
the clients are running at their respective threshold
frequencies to limit Cx peak current.

Change-Id: I5ffcf1a42523072d2b8b7bc0022eb3cc067acbb9
Signed-off-by: Rajesh Kemisetti <rajeshk@codeaurora.org>