drm/msm/dpu: Implement 10-bit color alpha for v12.0 DPU

v12.0 DPU on SM8750 comes with 10-bit color alpha.  Add register
differences and new implementations of setup_alpha_out(),
setup_border_color() and setup_blend_config().

Notable changes in v6:
Correct fg_alpha shift on new DPU, pointed out by Abel Vesas.

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/659629/
Link: https://lore.kernel.org/r/20250618-b4-sm8750-display-v7-10-a591c609743d@linaro.org


Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>