rtc: add EM3027 rtc driver

Add support for EM Microelectronic EM3027 RTC chip.

Signed-off-by: Mike Rapoport <mike@compulab.co.il>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>