rtc: pcf50633: consider alrm->enable in pcf50633_rtc_set_alarm

According to Documentation/rtc.txt, RTC_WKALM_SET sets the alarm time and
enables/disables the alarm.  We implement RTC_WKALM_SET through
pcf50633_rtc_set_alarm.  The enabling/disabling part was missing.

Signed-off-by: Werner Almesberger <werner@openmoko.org>
Reported-by: Michael 'Mickey' Lauer <mickey@openmoko.org>
Signed-off-by: Paul Fertser <fercerpav@gmail.com>
Cc: Paul Gortmaker <p_gortmaker@yahoo.com>
Cc: Balaji Rao <balajirrao@openmoko.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>