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/include/tinycrypt/ecc_dsa.h b/include/tinycrypt/ecc_dsa.h
index 349f061..e54a77e 100644
--- a/include/tinycrypt/ecc_dsa.h
+++ b/include/tinycrypt/ecc_dsa.h
@@ -1,11 +1,14 @@
 /* ecc_dh.h - TinyCrypt interface to EC-DSA implementation */
 
 /*
+ *  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:
  *