ARM: NUC900: add RTC driver support for nuc910 and nuc920

Signed-off-by: Wan ZongShun <mcuos.com@gmail.com>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Hu Ruihuan <specter118@gmail.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: "jack wang" <jack_wang@usish.com>
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>