Addition of copyright statements to tinycrypt files

Each of the tinycrypt files have had some very minor changes, so need a
copyright statement.
diff --git a/tinycrypt/ecc_dsa.c b/tinycrypt/ecc_dsa.c
index c093ebe..a3893d3 100644
--- a/tinycrypt/ecc_dsa.c
+++ b/tinycrypt/ecc_dsa.c
@@ -1,10 +1,13 @@
 /* ec_dsa.c - TinyCrypt implementation of EC-DSA */
 
+/*
+ *  Copyright (c) 2019, Arm Limited (or its affiliates), All Rights Reserved.
+ *  SPDX-License-Identifier: BSD-3-Clause
+ */
+
 /* Copyright (c) 2014, Kenneth MacKay
  * All rights reserved.
  *
- * SPDX-License-Identifier: BSD-3-Clause
- *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
  *  * Redistributions of source code must retain the above copyright notice,