drm/msm/dpu: make dpu_hw_ctl_clear_all_blendstages clear necessary LMs

dpu_hw_ctl_clear_all_blendstages() clears settings for the few first LMs
instead of mixers actually used for the CTL. Change it to clear
necessary data, using provided mixer ids.

Fixes: 25fdd593

 ("drm/msm: Add SDM845 DPU support")
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://lore.kernel.org/r/20210704230519.4081467-1-dmitry.baryshkov@linaro.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>