treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 435

Based on 1 normalized pattern(s):

  all code subject to the gpl version 2

extracted by the scancode license scanner the SPDX license identifier

  GPL-2.0-only

has been chosen to replace the boilerplate/reference in 1 file(s).
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Reviewed-by: NArmijn Hemel <armijn@tjaldur.nl>
Reviewed-by: NAllison Randal <allison@lohutok.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190531190114.938134445@linutronix.deSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

lib/show_mem.c

+// SPDX-License-Identifier: GPL-2.0-only
 /*
  * Generic show_mem() implementation
  *
  * Copyright (C) 2008 Johannes Weiner <hannes@saeurebad.de>
- * All code subject to the GPL version 2.
  */
 
 #include <linux/mm.h>