tools/virtio: fix build for 3.8

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
diff --git a/drivers/vhost/test.c b/drivers/vhost/test.c
index 91d6f06..329d302 100644
--- a/drivers/vhost/test.c
+++ b/drivers/vhost/test.c
@@ -275,7 +275,9 @@
 		return vhost_test_reset_owner(n);
 	default:
 		mutex_lock(&n->dev.mutex);
-		r = vhost_dev_ioctl(&n->dev, ioctl, arg);
+		r = vhost_dev_ioctl(&n->dev, ioctl, argp);
+                if (r == -ENOIOCTLCMD)
+                        r = vhost_vring_ioctl(&n->dev, ioctl, argp);
 		vhost_test_flush(n);
 		mutex_unlock(&n->dev.mutex);
 		return r;