msm: kgsl: Use the GMU for bus DCVS

The GMU firmware supports executing bus DCVS votes.
Add this capability using HFI.

Change-Id: I92595a8940c79d9dc9371b3d3801892a090a51e1
Signed-off-by: Carter Cooper <ccooper@codeaurora.org>
Signed-off-by: Kyle Piefer <kpiefer@codeaurora.org>