ARM: dts: BCM53573: Relicense Luxul files to the GPL 2.0+ / MIT

This matches licensing used by other BCM53573 files and BCM5301X.

Signed-off-by: Dan Haab <[e-mail]>
Acked-by: Rafał Miłecki <[e-mail]>
Signed-off-by: Florian Fainelli <[e-mail]>

arch/arm/boot/dts/bcm47189-luxul-xap-1440.dts

···
+// SPDX-License-Identifier: GPL-2.0-or-later OR MIT
 /*
  * Copyright 2017 Luxul Inc.
- *
- * Licensed under the ISC license.
  */
 
 /dts-v1/;

arch/arm/boot/dts/bcm47189-luxul-xap-810.dts

···
+// SPDX-License-Identifier: GPL-2.0-or-later OR MIT
 /*
  * Copyright 2017 Luxul Inc.
- *
- * Licensed under the ISC license.
  */
 
 /dts-v1/;