ARM: dts: BCM5301X: Relicense Buffalo files to the GPL 2.0+ / MIT

This matches licensing used by other BCM5301X files and is preferred as:
1) GPL 2.0+ makes is clearly compatible with Linux kernel
2) MIT is also permissive but preferred over ISC

These files were created and ever touched by a group of four people
only: Felix, INAGAKI, Hauke and me.
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Acked-by: Felix Fietkau <nbd@nbd.name>
Acked-by: INAGAKI Hiroshi <musashino.open@gmail.com>
Acked-by: Hauke Mehrtens <hauke@hauke-m.de>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>

arch/arm/boot/dts/bcm4708-buffalo-wzr-1750dhp.dts

+// SPDX-License-Identifier: GPL-2.0-or-later OR MIT
 /*
  * Broadcom BCM470X / BCM5301X ARM platform code.
  * DTS for Buffalo WZR-1750DHP
  *
  * Copyright (C) 2014 Rafał Miłecki <zajec5@gmail.com>
- *
- * Licensed under the GNU/GPL. See COPYING for details.
  */
 
 /dts-v1/;

arch/arm/boot/dts/bcm47081-buffalo-wzr-900dhp.dts

+// SPDX-License-Identifier: GPL-2.0-or-later OR MIT
 /*
  * Broadcom BCM470X / BCM5301X ARM platform code.
  * DTS for Buffalo WZR-900DHP
  *
  * Copyright (C) 2015 Rafał Miłecki <zajec5@gmail.com>
- *
- * Permission to use, copy, modify, and/or distribute this software for any
- * purpose with or without fee is hereby granted, provided that the above
- * copyright notice and this permission notice appear in all copies.
- *
- * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
- * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
- * AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
- * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
- * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
- * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
- * PERFORMANCE OF THIS SOFTWARE.
  */
 
 /dts-v1/;

arch/arm/boot/dts/bcm4709-buffalo-wxr-1900dhp.dts

+// SPDX-License-Identifier: GPL-2.0-or-later OR MIT
 /*
  * Broadcom BCM470X / BCM5301X ARM platform code.
  * DTS for Buffalo WXR-1900DHP
  *
  * Copyright (C) 2015 Felix Fietkau <nbd@openwrt.org>
- *
- * Licensed under the GNU/GPL. See COPYING for details.
  */
 
 /dts-v1/;