intel_th: Add SPDX GPL-2.0 header to replace GPLv2 boilerplate

This adds SPDX GPL-2.0 header to the Trace Hub driver and removes the
GPLv2 boilerplate text.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>

drivers/hwtracing/intel_th/gth.h

@@ -1,16 +1,8 @@
+/* SPDX-License-Identifier: GPL-2.0 */
 /*
  * Intel(R) Trace Hub Global Trace Hub (GTH) data structures
  *
  * Copyright (C) 2014-2015 Intel Corporation.
- *
- * This program is free software; you can redistribute it and/or modify it
- * under the terms and conditions of the GNU General Public License,
- * version 2, as published by the Free Software Foundation.
- *
- * This program is distributed in the hope 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.
  */
 
 #ifndef __INTEL_TH_GTH_H__