drm: msm: a6xx: send opp instead of a frequency

This patch changes the plumbing to send the devfreq recommended opp rather
than the frequency. Also consolidate and rearrange the code in a6xx to set
the GPU frequency and the icc vote in preparation for the upcoming
changes for GPU->DDR scaling votes.

Signed-off-by: Sharat Masetty <smasetty@codeaurora.org>
Signed-off-by: Akhil P Oommen <akhilpo@codeaurora.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>