treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 180

Based on 1 normalized pattern(s):

  subject to the gnu general public license 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 4 file(s).
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Steve Winslow <swinslow@gmail.com>
Reviewed-by: Richard Fontana <rfontana@redhat.com>
Reviewed-by: Armijn Hemel <armijn@tjaldur.nl>
Reviewed-by: Allison Randal <allison@lohutok.net>
Reviewed-by: Alexios Zavras <alexios.zavras@intel.com>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190528170026.343113277@linutronix.deSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/x86/entry/vsyscall/vsyscall_emu_64.S

+/* SPDX-License-Identifier: GPL-2.0-only */
 /*
  * vsyscall_emu_64.S: Vsyscall emulation page
  *
  * Copyright (c) 2011 Andy Lutomirski
- *
- * Subject to the GNU General Public License, version 2
  */
 
 #include <linux/linkage.h>

arch/x86/include/asm/vvar.h

+/* SPDX-License-Identifier: GPL-2.0-only */
 /*
  * vvar.h: Shared vDSO/kernel variable declarations
  * Copyright (c) 2011 Andy Lutomirski
- * Subject to the GNU General Public License, version 2
  *
  * A handful of variables are accessible (read-only) from userspace
  * code in the vsyscall page and the vdso.  They are declared here.

tools/testing/selftests/vDSO/vdso_standalone_test_x86.c

+// SPDX-License-Identifier: GPL-2.0-only
 /*
  * vdso_test.c: Sample code to test parse_vdso.c on x86
  * Copyright (c) 2011-2014 Andy Lutomirski
- * Subject to the GNU General Public License, version 2
  *
  * You can amuse yourself by compiling with:
  * gcc -std=gnu99 -nostdlib

tools/testing/selftests/vDSO/vdso_test.c

+// SPDX-License-Identifier: GPL-2.0-only
 /*
  * vdso_test.c: Sample code to test parse_vdso.c
  * Copyright (c) 2014 Andy Lutomirski
- * Subject to the GNU General Public License, version 2
  *
  * Compile with:
  * gcc -std=gnu99 vdso_test.c parse_vdso.c