i2c: i2c-cros-ec-tunnel: Switch to SPDX identifier.

Adopt the SPDX license identifier headers to ease license compliance
management.
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

drivers/i2c/busses/i2c-cros-ec-tunnel.c

-/*
- *  Copyright (C) 2013 Google, Inc
- *
- *  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; either version 2 of the License, or
- *  (at your option) any later version.
- *
- * Expose an I2C passthrough to the ChromeOS EC.
- */
+// SPDX-License-Identifier: GPL-2.0+
+// Expose an I2C passthrough to the ChromeOS EC.
+//
+// Copyright (C) 2013 Google, Inc.
 
 #include <linux/module.h>
 #include <linux/i2c.h>