ARM: dts: am335x-shc.dts: Switch to SPDX identifier

Adopt the SPDX license identifier headers to ease license
compliance management.
Signed-off-by: Heiko Schocher <hs@denx.de>
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/boot/dts/am335x-shc.dts

+// SPDX-License-Identifier: GPL-2.0
 /*
  * support for the bosch am335x based shc c3 board
  *
  * Copyright, C) 2015 Heiko Schocher <hs@denx.de>
  *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2 as
- * published by the Free Software Foundation.
  */
 /dts-v1/;