VSOCK: add SPDX identifiers to vsock tests

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/tools/testing/vsock/control.h b/tools/testing/vsock/control.h
index 54a07ef..dac3964 100644
--- a/tools/testing/vsock/control.h
+++ b/tools/testing/vsock/control.h
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
 #ifndef CONTROL_H
 #define CONTROL_H