rtc: rtc-s3c: Updates driver for S3C64XX and newer SoCs

This Patch does followings.
1) Enables support for alarm and time tick pending register
   for periodic interrupt generation.
2) Changes writeb to writew beacuse the macro S3C64XX_RTCCON_TICEN
   (Tick Timer Enable) is 9th bit of register.
3) Changes writeb to writel as max_user_freq used in s3c64xx is 32768 and
   requires 15 bits to update the Tick Count Register.

Signed-off-by: Atul Dahiya <atul.dahiya@samsung.com>
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>