ARM: dts: imx: Switch NXP boards to SPDX identifier

Adopt the SPDX license identifier headers to ease license compliance
management.

Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx35-pdk.dts

@@ -1,14 +1,7 @@
-/*
- * Copyright 2013 Eukréa Electromatique <denis@eukrea.com>
- * Copyright 2014 Freescale Semiconductor, Inc.
- *
- * 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 2013 Eukréa Electromatique <denis@eukrea.com>
+// Copyright 2014 Freescale Semiconductor, Inc.
 
 /dts-v1/;
 #include "imx35.dtsi"