rtc: rtc-s3c: Add BCD register initialization codes

RTC needs to be initialized when BCD registers have invalid value.

Signed-off-by: Taekgyun Ko <taeggyun.ko@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>
Cc: Ben Dooks <ben-linux@fluff.org>
Acked-by: Alessandro Zummo <a.zummo@towertech.it>