Platform real time clock driver for Dallas 1511 chip

Add RTC support for DS1511 RTC/WDT chip.

Signed-off-by: Andy Sharp <andy.sharp@onstor.com>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>