gpio: xlp: Cut down on boilerplate

Just use the SPDX license tag for this file.

Cc: Kamlakant Patel <kamlakant.patel@cavium.com>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpio-xlp.c

+// SPDX-License-Identifier: GPL-2.0
 /*
  * Copyright (C) 2003-2015 Broadcom Corporation
  * All Rights Reserved
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2 as
- * published by the Free Software Foundation.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
  */
 
 #include <linux/gpio/driver.h>