drm/atomic: Don't pollute crtc_state->mode_blob with error pointers

Make sure we don't assign an error pointer to crtc_state->mode_blob
as that will break all kinds of places that assume either NULL or a
valid pointer (eg. drm_property_blob_put()).

Cc: stable@vger.kernel.org
Reported-by: fuyufan <fuyufan@huawei.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220209091928.14766-1-ville.syrjala@linux.intel.com


Acked-by: Maxime Ripard <maxime@cerno.tech>