virtio/tools: add delayed interupt mode

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
diff --git a/tools/virtio/linux/virtio.h b/tools/virtio/linux/virtio.h
index 7579f19..81847dd 100644
--- a/tools/virtio/linux/virtio.h
+++ b/tools/virtio/linux/virtio.h
@@ -203,6 +203,7 @@
 void virtqueue_disable_cb(struct virtqueue *vq);
 
 bool virtqueue_enable_cb(struct virtqueue *vq);
+bool virtqueue_enable_cb_delayed(struct virtqueue *vq);
 
 void *virtqueue_detach_unused_buf(struct virtqueue *vq);
 struct virtqueue *vring_new_virtqueue(unsigned int num,