tools/virtio:Fix the wrong format specifier

The unsigned int should use "%u" instead of "%d".
Signed-off-by: Zhu Jun <zhujun2@cmss.chinamobile.com>
Message-Id: <20240724074108.9530-1-zhujun2@cmss.chinamobile.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Eugenio Pérez <eperezma@redhat.com>
Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>

tools/virtio/ringtest/main.c

@@ -276,7 +276,7 @@ static void help(void)
 	fprintf(stderr, "Usage: <test> [--help]"
 		" [--host-affinity H]"
 		" [--guest-affinity G]"
-		" [--ring-size R (default: %d)]"
+		" [--ring-size R (default: %u)]"
 		" [--run-cycles C (default: %d)]"
 		" [--batch b]"
 		" [--outstanding o]"