treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 479

Based on 1 normalized pattern(s):

  released under the gpl v2 based on gplv2 source code

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: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Allison Randal <allison@lohutok.net>
Reviewed-by: Enrico Weigelt <info@metux.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190604081204.281377867@linutronix.deSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tools/perf/util/genelf_debug.c

+// SPDX-License-Identifier: GPL-2.0-only
 /*
  * genelf_debug.c
  * Copyright (C) 2015, Google, Inc
@@ -5,8 +6,6 @@
  * Contributed by:
  * 	Stephane Eranian <eranian@google.com>
  *
- * Released under the GPL v2.
- *
  * based on GPLv2 source code from Oprofile
  * @remark Copyright 2007 OProfile authors
  * @author Philippe Elie