drm/msm/mdss: correct UBWC programming for SM8550

The SM8550 platform employs newer UBWC decoder, which requires slightly
different programming.

Fixes: a2f33995 ("drm/msm: mdss: add support for SM8550")
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/550049/
Link: https://lore.kernel.org/r/20230728213320.97309-2-dmitry.baryshkov@linaro.org