Add SPDX-License-Identifier: MIT to MIT licensed files.

portable/IAR/ARM_CM33/non_secure/port.c

diff --git a/portable/IAR/ARM_CM33/non_secure/port.c b/portable/IAR/ARM_CM33/non_secure/port.c
index 7a066ae..5c5c7d8 100644
--- a/portable/IAR/ARM_CM33/non_secure/port.c
+++ b/portable/IAR/ARM_CM33/non_secure/port.c
@@ -2,6 +2,8 @@
  * FreeRTOS Kernel <DEVELOPMENT BRANCH>

  * Copyright (C) 2021 Amazon.com, Inc. or its affiliates.  All Rights Reserved.

  *

+ * SPDX-License-Identifier: MIT
+ *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of

  * this software and associated documentation files (the "Software"), to deal in

  * the Software without restriction, including without limitation the rights to