rtc: pcf85363: convert to SPDX identifier

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

drivers/rtc/rtc-pcf85363.c

+// SPDX-License-Identifier: GPL-2.0
 /*
  * drivers/rtc/rtc-pcf85363.c
  *
  * Driver for NXP PCF85363 real-time clock.
  *
  * Copyright (C) 2017 Eric Nelson
- *
- * 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.
- *
- * Based loosely on rtc-8583 by Russell King, Wolfram Sang and Juergen Beisert
  */
 #include <linux/module.h>
 #include <linux/i2c.h>