drm/msm/dpu: Fix for non-visible planes

Fixes `kms_cursor_crc --run-subtest cursor-offscreen`.. when the cursor
moves offscreen the plane becomes non-visible, so we need to skip over
it in crtc atomic test and mixer setup.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Fixes: 25fdd593

 ("drm/msm: Add SDM845 DPU support")
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Patchwork: https://patchwork.freedesktop.org/patch/492819/
Link: https://lore.kernel.org/r/20220707212003.1710163-1-robdclark@gmail.com