rtc-s3c: add variants for S3C2443 and S3C2416

Especially the TICNT registers are different from the two rtc
types that currently exists.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Acked-by: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>