drm/msm/dpu: get rid of cached flush_mask

Instead of querying the CTL for the flush mask (for SSPP, LM or DSPP),
storing the mask in the mixer configuration and then pushing the mask to
the CTL, tell CTL to cache the flush in place.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Patchwork: https://patchwork.freedesktop.org/patch/473159/
Link: https://lore.kernel.org/r/20220209172520.3719906-9-dmitry.baryshkov@linaro.org


Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>