rtc: add Freescale MC13783 RTC driver

This driver provides support for the RTC part integrated into the
Freescale MC13783 PMIC and bases on patch created earlier by Sascha
Hauer.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-by: Valentin Longchamp <valentin.longchamp@epfl.ch>
Cc: Paul Gortmaker <p_gortmaker@yahoo.com>
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>