rtc: convert core to SPDX identifier

Use SPDX-License-Identifier instead of a verbose license text. Also fix the
block comment alignment.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

drivers/rtc/hctosys.c

@@ -1,13 +1,10 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * RTC subsystem, initialize system time on startup
  *
  * Copyright (C) 2005 Tower Technologies
  * Author: Alessandro Zummo <a.zummo@towertech.it>
- *
- * 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.
-*/
+ */
 
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt