rtc: wm831x: convert to SPDX identifier

Use SPDX-License-Identifier instead of a verbose license text.
Acked-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

drivers/rtc/rtc-wm831x.c

+// SPDX-License-Identifier: GPL-2.0+
 /*
  *	Real Time Clock driver for Wolfson Microelectronics WM831x
  *
@@ -5,11 +6,6 @@
  *
  *  Author: Mark Brown <broonie@opensource.wolfsonmicro.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;  either version 2 of the  License, or (at your
- *  option) any later version.
- *
  */
 
 #include <linux/module.h>