treewide: Replace GPLv2 boilerplate/reference with SPDX - gpl-2.0_391.RULE

Based on the normalized pattern:

    this software file (the file ) is distributed by nxp under the terms
    of the gnu general public license version 2 june 1991 (the license )
    you may use redistribute and/or modify this file in accordance with
    the terms and conditions of the license a copy of which is available
    by writing to the free software foundation inc 51 franklin street
    fifth floor boston ma 02110-1301 usa or on the worldwide web at
    http://www

 gnu org/licenses/old-licenses/gpl-2 0 txt  the file is
    distributed as-is without warranty of any kind and the implied
    warranties of merchantability or fitness for a particular purpose are
    expressly disclaimed the license provides additional details about
    this warranty disclaimer

extracted by the scancode license scanner the SPDX license identifier

    GPL-2.0-only

has been chosen to replace the boilerplate/reference.

Reviewed-by: Allison Randal <allison@lohutok.net>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>