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: Ibb7ed1e4e2191b9a978e26b5bacf916db403a60e
diff --git a/ArmnnDriverImpl.hpp b/ArmnnDriverImpl.hpp
index 87da581..fbfbc43 100644
--- a/ArmnnDriverImpl.hpp
+++ b/ArmnnDriverImpl.hpp
@@ -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
 //
 
 #pragma once