soc: actions: Convert to SPDX license identifiers

Replace textual license notices with SPDX-License-Identifier lines.
Add an SPDX-License-Identifier for the Makefile.
Signed-off-by: Andreas Färber <afaerber@suse.de>

drivers/soc/actions/Makefile

+# SPDX-License-Identifier: GPL-2.0+
+
 obj-$(CONFIG_OWL_PM_DOMAINS_HELPER) += owl-sps-helper.o
 obj-$(CONFIG_OWL_PM_DOMAINS) += owl-sps.o

drivers/soc/actions/owl-sps-helper.c

+// SPDX-License-Identifier: GPL-2.0+
 /*
  * Actions Semi Owl Smart Power System (SPS) shared helpers
  *
@@ -5,11 +6,6 @@
  * Author: Actions Semi, Inc.
  *
  * Copyright (c) 2017 Andreas Färber
- *
- * This program is free software; you can redistribute  it and/or modify it
- * under  the terms of  the GNU General  Public License as published by the
- * Free Software Foundation;  either version 2 of the  License, or (at your
- * option) any later version.
  */
 
 #include <linux/delay.h>

drivers/soc/actions/owl-sps.c

+// SPDX-License-Identifier: GPL-2.0+
 /*
  * Actions Semi Owl Smart Power System (SPS)
  *
@@ -5,11 +6,6 @@
  * Author: Actions Semi, Inc.
  *
  * Copyright (c) 2017 Andreas Färber
- *
- * This program is free software; you can redistribute  it and/or modify it
- * under  the terms of  the GNU General  Public License as published by the
- * Free Software Foundation;  either version 2 of the  License, or (at your
- * option) any later version.
  */
 
 #include <linux/of_address.h>