hwmon: (sht15) Switch to SPDX identifier

Adopt the SPDX license identifier headers to ease license compliance
management.
Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/sht15.c

+// SPDX-License-Identifier: GPL-2.0
 /*
  * sht15.c - support for the SHT15 Temperature and Humidity Sensor
  *
@@ -9,10 +10,6 @@
  *
  * Copyright (c) 2007 Wouter Horre
  *
- * 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.
- *
  * For further information, see the Documentation/hwmon/sht15 file.
  */