Add SPDX annotation

Related: OS#3515
Change-Id: I3719bd8dc015569ecd81928fc079e27593cdca09
diff --git a/Transceiver52M/arch/common/convolve_base.c b/Transceiver52M/arch/common/convolve_base.c
index 9bb8d3d..bfda783 100644
--- a/Transceiver52M/arch/common/convolve_base.c
+++ b/Transceiver52M/arch/common/convolve_base.c
@@ -2,6 +2,8 @@
  * Convolution
  * Copyright (C) 2012, 2013 Thomas Tsou <tom@tsou.cc>
  *
+ * SPDX-License-Identifier: LGPL-2.1+
+ *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either