IVGCVSW-1807 : change license text in file headers

All changes are the same:

   //
   // Copyright © 2017 ARM Ltd. All rights reserved.
  -// See LICENSE file in the project root for full license information.
  +// SPDX-License-Identifier: MIT
   //

Change-Id: I37eae011411133663ca9d2b059714d92f8bf8e24
diff --git a/src/armnn/test/RuntimeTests.cpp b/src/armnn/test/RuntimeTests.cpp
index e29a1d4..0c896d8 100644
--- a/src/armnn/test/RuntimeTests.cpp
+++ b/src/armnn/test/RuntimeTests.cpp
@@ -1,6 +1,6 @@
 //
 // Copyright © 2017 Arm Ltd. All rights reserved.
-// See LICENSE file in the project root for full license information.
+// SPDX-License-Identifier: MIT
 //
 #include <boost/test/unit_test.hpp>