msm: mdss: Compute dma vote for mdp core clk based on resolution

On 8909 PLs, the clock vote from dma client is hardcoded to 160Mhz
resulting in higher clock throughout the execution. The current changes
target reduction in the clock by computing it based on the panel resolution
and refresh rate.

Change-Id: I71621a102618cd6c8a5ad6dc318cf3c63a13dce3
Signed-off-by: Sravanthi Kollukuduru <skolluku@codeaurora.org>