drm/msm/dsi: Reuse earlier computed dsc->slice_chunk_size

drm/msm/dsi: Reuse earlier computed dsc->slice_chunk_size

dsi_populate_dsc_params() is called prior to dsi_update_dsc_timing() and
already computes a value for slice_chunk_size, whose value doesn't need
to be recomputed and re-set here.

Fixes: 08802f515c3c ("drm/msm/dsi: Add support for DSC configuration")
Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Marijn Suijten <marijn.suijten@somainline.org>
Patchwork: https://patchwork.freedesktop.org/patch/508934/
Link: https://lore.kernel.org/r/20221026182824.876933-5-marijn.suijten@somainline.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>