tools/virtio: add device, device_driver stubs

Add stubs needed by virtio.h

Message-ID: <0fabf13f6ea812ebc73b1c919fb17d4dec1545db.1764873799.git.mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
1 file changed