rtc: ab-b5ze-s3: 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-ab-b5ze-s3.c

+// SPDX-License-Identifier: GPL-2.0+
 /*
  * rtc-ab-b5ze-s3 - Driver for Abracon AB-RTCMC-32.768Khz-B5ZE-S3
  *                  I2C RTC / Alarm chip
@@ -10,15 +11,6 @@
  *
  * This work is based on ISL12057 driver (drivers/rtc/rtc-isl12057.c).
  *
- * 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.
- *
- * This program is distributed in the hope that 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.
  */
 
 #include <linux/module.h>