drm/msm/dpu: Defer SSPP allocation until CRTC check

drm/msm/dpu: Defer SSPP allocation until CRTC check

Currently, mapping plane to SSPP occurs during the plane check phase for
non-virtual plane case. The SSPP allocation and plane mapping occurs during
CRTC check phase for virtual plane case. Defer these SSPP operations until
CRTC check stage to unify the 2 cases, and ease later revisement for
quad-pipe change.

Signed-off-by: Jun Nie <jun.nie@linaro.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Patchwork: https://patchwork.freedesktop.org/patch/711322/
Link: https://lore.kernel.org/r/20260312-msm-next-quad-pipe-split-v19-2-4ffa2b06c996@linaro.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>