msm/drm/dsi: Round up DSC hdisplay calculation

Currently, when compression is enabled, hdisplay is reduced via integer
division. This causes issues for modes where the original hdisplay is
not a multiple of 3.

To fix this, use DIV_ROUND_UP to divide hdisplay.

Suggested-by: Marijn Suijten <marijn.suijten@somainline.org>
Fixes: 08802f51 ("drm/msm/dsi: Add support for DSC configuration")
Reviewed-by: Marijn Suijten <marijn.suijten@somainline.org>
Signed-off-by: Jessica Zhang <quic_jesszhan@quicinc.com>
Patchwork: https://patchwork.freedesktop.org/patch/541970/
Link: https://lore.kernel.org/r/20230405-add-dsc-support-v6-1-95eab864d1b6@quicinc.com


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