of: Use SPDX license tag for DT files

Convert remaining DT files to use SPDX-License-Identifier tags.

Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
Reviewed-by: Frank Rowand <frank.rowand@sony.com>
Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com>
Signed-off-by: Rob Herring <robh@kernel.org>
diff --git a/drivers/of/address.c b/drivers/of/address.c
index fa6cabf..6391604 100644
--- a/drivers/of/address.c
+++ b/drivers/of/address.c
@@ -1,4 +1,4 @@
-
+// SPDX-License-Identifier: GPL-2.0
 #define pr_fmt(fmt)	"OF: " fmt
 
 #include <linux/device.h>