arm64: dts: mediatek: Switch to SPDX license identifier for MT6797 SoC

Switch to SPDX license identifier for MT6797 SoC.
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Link: https://lore.kernel.org/r/20200222162444.11590-5-manivannan.sadhasivam@linaro.orgSigned-off-by: Matthias Brugger <matthias.bgg@gmail.com>

arch/arm64/boot/dts/mediatek/mt6797.dtsi

+// SPDX-License-Identifier: GPL-2.0
 /*
  * Copyright (c) 2017 MediaTek Inc.
  * Author: Mars.C <mars.cheng@mediatek.com>
- *
- * 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.
- *
- * This program is distributed in the hope that it will be useful,
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
  */
 
 #include <dt-bindings/clock/mt6797-clk.h>