drm/virtio: plane: use drm managed resources

Use drm managed resource allocation (drmm_universal_plane_alloc()) in
order to cleanup/simplify drm plane .destroy callback.

Signed-off-by: Danilo Krummrich <dakr@redhat.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20220714130028.2127858-2-dakr@redhat.com


Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>