drivers/rtc/rtc-ab8500.c: use UIE emulation

RTC: Fix to correct improper implementation of clock update irq
(RTC_UIE) and enable UIE Emulation.

[akpm@linux-foundation.org: checkpatch fixes]
Signed-off-by: Ramesh Chandrasekaran <ramesh.chandrasekaran@stericsson.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>