drm/msm/dsi: Reduce pclk rate for compression

Adjust the pclk rate to divide hdisplay by the compression ratio when DSC
is enabled.

Signed-off-by: Jessica Zhang <quic_jesszhan@quicinc.com>
Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Patchwork: https://patchwork.freedesktop.org/patch/541972/
Link: https://lore.kernel.org/r/20230405-add-dsc-support-v6-2-95eab864d1b6@quicinc.com


Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>