platform/x86: intel_mid_powerbtn: Convert to use SPDX identifier

// SPDX-License-Identifier: GPL-2.0

/*

 * Power button driver for Intel MID platforms.

 *

 *

 * Author: Hong Liu <hong.liu@intel.com>

 * Author: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License as published by

 * the Free Software Foundation; version 2 of the License.

 *

 * 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/input.h>