RTC: add missing "return 0" in new alarm func for rtc-bfin.c

The new bfin_rtc_alarm_irq_enable function forgot to add a "return 0" to
the end leading to the build warning:
	drivers/rtc/rtc-bfin.c: In function 'bfin_rtc_alarm_irq_enable':
	drivers/rtc/rtc-bfin.c:253: warning: control reaches end of non-void function

CC: stable@kernel.org
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: NMike Frysinger <vapier@gentoo.org>
Signed-off-by: NJohn Stultz <john.stultz@linaro.org>

drivers/rtc/rtc-bfin.c

@@ -250,6 +250,8 @@ static int bfin_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
 		bfin_rtc_int_set_alarm(rtc);
 	else
 		bfin_rtc_int_clear(~(RTC_ISTAT_ALARM | RTC_ISTAT_ALARM_DAY));
+
+	return 0;
 }
 
 static int bfin_rtc_read_time(struct device *dev, struct rtc_time *tm)