chore: update to use Arm word across TF-A

Align entire TF-A to use Arm in copyright header.

Change-Id: Ief9992169efdab61d0da6bd8c5180de7a4bc2244
Signed-off-by: Govindraj Raja <govindraj.raja@arm.com>
diff --git a/lib/extensions/amu/amu_private.h b/lib/extensions/amu/amu_private.h
index eb7ff0e..a3b6845 100644
--- a/lib/extensions/amu/amu_private.h
+++ b/lib/extensions/amu/amu_private.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017-2021, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2017-2021, Arm Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */