treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 53

Based on 1 normalized pattern(s):

this code may be copied under the gpl v 2 or at your option any
later version

extracted by the scancode license scanner the SPDX license identifier

GPL-2.0-or-later

has been chosen to replace the boilerplate/reference in 1 file(s).

Signed-off-by: Thomas Gleixner <[e-mail]>
Reviewed-by: Richard Fontana <[e-mail]>
Reviewed-by: Kate Stewart <[e-mail]>
Reviewed-by: Allison Randal <[e-mail]>
Cc: [e-mail]
Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

net/decnet/netfilter/dn_rtmsg.c

···
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * DECnet       An implementation of the DECnet protocol suite for the LINUX
  *              operating system.  DECnet is implemented using the  BSD Socket
···
  *              DECnet Routing Message Grabulator
  *
  *              (C) 2000 ChyGwyn Limited  -  http://www.chygwyn.com/
- *              This code may be copied under the GPL v.2 or at your option
- *              any later version.
  *
  * Author:      Steven Whitehouse <[e-mail]>
- *
  */
 #include <linux/module.h>
 #include <linux/skbuff.h>