rtc: Ramtron FM3130 RTC support

Ramtron FM3130 is a chip with two separate devices inside, RTC clock and
FRAM.  This driver provides only RTC functionality.

This chip is met in lots of custom boards with AT91SAMXXXX CPU I work
with, is cheap and in no way better or worse than any other RTC on market.
 While it is mostly met on much smaller devices, I think it is great to
have it supported in Linux.

Signed-off-by: Sergey Lapin <slapin@ossfans.org>
Signed-off-by: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>