Add a watchdog driver interface to rtc-m41t80 driver.  This is derived from
works by Alexander Bigga <ab@mycable.de>
Signed-off-by: NAtsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: NAlexander Bigga <ab@mycable.de>
Cc: David Brownell <david-b@pacbell.net>
Acked-by: NAlessandro Zummo <a.zummo@towertech.it>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>