platform/x86: intel-wmi-thunderbolt: Convert to use SPDX identifier

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

No functional change.

While here, correct MODULE_LICENSE() string to be aligned with license text.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

drivers/platform/x86/intel-wmi-thunderbolt.c

+// SPDX-License-Identifier: GPL-2.0
 /*
  * WMI Thunderbolt driver
  *
  * Copyright (C) 2017 Dell Inc. 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.
  */
 
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
@@ -95,4 +87,4 @@ module_wmi_driver(intel_wmi_thunderbolt_driver);
 MODULE_ALIAS("wmi:" INTEL_WMI_THUNDERBOLT_GUID);
 MODULE_AUTHOR("Mario Limonciello <mario.limonciello@dell.com>");
 MODULE_DESCRIPTION("Intel WMI Thunderbolt force power driver");
-MODULE_LICENSE("GPL");
+MODULE_LICENSE("GPL v2");