drm/virtio: Handle drm_crtc_init_with_planes() errors

drm/virtio: Handle drm_crtc_init_with_planes() errors

Return value of function drm_crtc_init_with_planes(),
called by vgdev_output_init(), is not checked,
but it is usually checked for this function.

Found by Linux Verification Center (linuxtesting.org) with SVACE.
Signed-off-by: Alexandr Sapozhnikov <alsp705@gmail.com>
Reviewed-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
[dmitry.osipenko@collabora.com: coding style fix, edit commit message]
Link: https://lore.kernel.org/r/20250922144418.41-1-alsp705@gmail.com