drm/msm/dpu: enable writeback on SM8150

Enable WB2 hardware block, enabling writeback support on this platform.

Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Patchwork: https://patchwork.freedesktop.org/patch/570192/
Link: https://lore.kernel.org/r/20231203003203.1293087-2-dmitry.baryshkov@linaro.org


[DB: picked up WB_SDM845_MASK from sdm845 patch]
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>