Update Arm copyright years thru 2021

The copyright for Arm, Ltd. is out of date.

Signed-off-by: Rob Herring <[email protected]>

Author: robherring

LICENSE

@@ -187,7 +187,7 @@
       same "printed page" as the copyright notice for easier
       identification within third-party archives.
 
-   Copyright 2016,2017 Arm, Ltd.
+   Copyright 2016-2021 Arm, Ltd.
    Copyright 2016,2017 Linaro, Ltd.
    Copyright 2008,2011 Power.org, Inc
    Copyright 2008,2011 Freescale Semiconductor, Inc.

source/license.rst

@@ -6,7 +6,7 @@
 | Copyright 2008,2011 Freescale Semiconductor, Inc.
 | Copyright 2008,2011 International Business Machines Corporation.
 | Copyright 2016,2017 Linaro, Ltd.
-| Copyright 2016,2017 Arm, Ltd.
+| Copyright 2016-2021 Arm, Ltd.
 
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