gpio: sch: 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-sch.c

+// SPDX-License-Identifier: GPL-2.0
 /*
  * GPIO interface for Intel Poulsbo SCH
  *
  *  Copyright (c) 2010 CompuLab Ltd
  *  Author: Denis Turischev <denis@compulab.co.il>
- *
- *  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.
- *
- *  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.
- *
- *  You should have received a copy of the GNU General Public License
- *  along with this program; see the file COPYING.  If not, write to
- *  the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
 #include <linux/acpi.h>
@@ -234,5 +222,5 @@ module_platform_driver(sch_gpio_driver);
 
 MODULE_AUTHOR("Denis Turischev <denis@compulab.co.il>");
 MODULE_DESCRIPTION("GPIO interface for Intel Poulsbo SCH");
-MODULE_LICENSE("GPL");
+MODULE_LICENSE("GPL v2");
 MODULE_ALIAS("platform:sch_gpio");