drm/msm/dpu: program correct register for UBWC config on DPU 8.x+

drm/msm/dpu: program correct register for UBWC config on DPU 8.x+

Since DPU 8.0 there is a separate register for the second rectangle,
which needs to be programmed with the UBWC config if multirect is being
used. Write pipe's UBWC configuration to the correct register.

Fixes: 100d7ef6995d ("drm/msm/dpu: add support for SM8450")
Tested-by: Val Packett <val@packett.cool> # x1e80100-dell-latitude-7455
Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Patchwork: https://patchwork.freedesktop.org/patch/699277/
Link: https://lore.kernel.org/r/20260119-msm-ubwc-fixes-v4-3-0987acc0427f@oss.qualcomm.com