arm64: dts: actions: Convert to new-style SPDX license identifiers

Move SPDX-License-Identifier to the top and add one for the Makefile.
Signed-off-by: Andreas Färber <afaerber@suse.de>

arch/arm64/boot/dts/actions/Makefile

+# SPDX-License-Identifier: GPL-2.0+
+
 dtb-$(CONFIG_ARCH_ACTIONS) += s700-cubieboard7.dtb
 
 dtb-$(CONFIG_ARCH_ACTIONS) += s900-bubblegum-96.dtb

arch/arm64/boot/dts/actions/s900-bubblegum-96.dts

+// SPDX-License-Identifier: (GPL-2.0+ OR MIT)
 /*
  * Copyright (c) 2017 Andreas Färber
- *
- * SPDX-License-Identifier: (GPL-2.0+ OR MIT)
  */
 
 /dts-v1/;

arch/arm64/boot/dts/actions/s900.dtsi

+// SPDX-License-Identifier: (GPL-2.0+ OR MIT)
 /*
  * Copyright (c) 2017 Andreas Färber
- *
- * SPDX-License-Identifier: (GPL-2.0+ OR MIT)
  */
 
 #include <dt-bindings/interrupt-controller/arm-gic.h>