Don't mask rtc-twl4030 alarm interrupts on shutdown

A triggering RTC alarm should be able to power on a device that has been
powered off. This patch enables that on twl4030 by not masking the alarm
interrupt at shutdown.

Signed-off-by: Matti Halme <matti.halme@nokia.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>