Move the bus clock to mdp device node,in order
to facilitate bus band width scaling on sc7180
target.

The parent device MDSS will not vote for bus bw,
instead the vote will be triggered by mdp device
node. Since a minimum vote is required to turn
on bus clock, move the clock node to mdp device
from where the votes are requested.

This patch has dependency on the below series
https://patchwork.kernel.org/patch/11468783/Reviewed-by: Rob Clark <robdclark@chromium.org>
Signed-off-by: Krishna Manikandan <mkrishn@codeaurora.org>
Link: https://lore.kernel.org/r/1594899334-19772-2-git-send-email-kalyan_t@codeaurora.orgSigned-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>