rtc: sc27xx: Fix format of SPDX identifier

For C files, use the C99 format (//).

Cc: Orson Zhai <orsonzhai@gmail.com>
Cc: Baolin Wang <baolin.wang7@gmail.com>
Cc: Chunyan Zhang <zhang.lyra@gmail.com>
Signed-off-by: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20210707075804.337458-6-nobuhiro1.iwamatsu@toshiba.co.jp

drivers/rtc/rtc-sc27xx.c

+// SPDX-License-Identifier: GPL-2.0
 /*
  * Copyright (C) 2017 Spreadtrum Communications Inc.
  *
- * SPDX-License-Identifier: GPL-2.0
  */
 
 #include <linux/bitops.h>