drm/msm/dpu: always use mdp device to scale bandwidth

Currently DPU driver scales bandwidth and core clock for sc7180 only,
while the rest of chips get static bandwidth votes. Make all chipsets
scale bandwidth and clock per composition requirements like sc7180 does.
Drop old voting path completely.

Tested on RB3 (SDM845) and RB5 (SM8250).

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://lore.kernel.org/r/20210401020533.3956787-2-dmitry.baryshkov@linaro.org
Signed-off-by: Rob Clark <robdclark@chromium.org>