rtc-mv: add support for Alarm

This patch adds the Alarm support, this mode enabled when adding
IORESOURCE_IRQ to the platform device resources.

The patch also enables the wakeup mode, so the wakealarm sysfs file (under
/sys/class/rtc/rtcX/) can be used to configure the alarm clock.

Signed-off-by: Saeed Bishara <saeed@marvell.com>
Signed-off-by: Nicolas Pitre <nico@marvell.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>