ARM: dts: imx53: Switch to SPDX identifier

Adopt the SPDX license identifier headers to ease license compliance
management.
Signed-off-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx53.dtsi

-/*
- * Copyright 2011 Freescale Semiconductor, Inc.
- * Copyright 2011 Linaro Ltd.
- *
- * The code contained herein is licensed under the GNU General Public
- * License. You may obtain a copy of the GNU General Public License
- * Version 2 or later at the following locations:
- *
- * http://www.opensource.org/licenses/gpl-license.html
- * http://www.gnu.org/copyleft/gpl.html
- */
+// SPDX-License-Identifier: GPL-2.0+
+//
+// Copyright 2011 Freescale Semiconductor, Inc.
+// Copyright 2011 Linaro Ltd.
 
 #include "imx53-pinfunc.h"
 #include <dt-bindings/clock/imx5-clock.h>