msm: kgsl: Ensure that power constraints run for a full interval

Make sure that a power constraint is given a full DCVS interval to
influence the GPU before having it adjusted back down.

Change-Id: Ic0dedbad22e74ce6e62e26c386b900442d7bab40
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>