gpio: sodaville: Convert to use SPDX identifier

Reduce size of duplicated comments by switching to use SPDX identifier.

No functional change.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

drivers/gpio/gpio-sodaville.c

+// SPDX-License-Identifier: GPL-2.0
 /*
  *  GPIO interface for Intel Sodaville SoCs.
  *
  *  Copyright (c) 2010, 2011 Intel Corporation
  *
  *  Author: Hans J. Koch <hjk@linutronix.de>
- *
- *  This program is free software; you can redistribute it and/or modify
- *  it under the terms of the GNU General Public License 2 as published
- *  by the Free Software Foundation.
- *
  */
 
 #include <linux/errno.h>