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>

drivers/of/pdt.c

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0+
 /* pdt.c: OF PROM device tree support code.
  *
  * Paul Mackerras	August 1996.
@@ -8,11 +9,6 @@
  *
  *  Adapted for sparc by David S. Miller davem@davemloft.net
  *  Adapted for multiple architectures by Andres Salomon <dilinger@queued.net>
- *
- *      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/kernel.h>