rtc: interface: Ensure alarm irq is enabled when UIE is enabled

When setting a normal alarm, user-space is responsible for using
RTC_AIE_ON/RTC_AIE_OFF to control if alarm irq should be enabled.

But when RTC_UIE_ON is used, interrupts must be enabled so that the
requested irq events are generated.
When RTC_UIE_OFF is used, alarm irq is disabled if there are no other
alarms queued, so this commit brings symmetry to that.

Signed-off-by: Esben Haabendal <esben@geanix.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20250516-rtc-uie-irq-fixes-v2-5-3de8e530a39e@geanix.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

Author: esben

drivers/rtc/interface.c

@@ -617,6 +617,10 @@ int rtc_update_irq_enable(struct rtc_device *rtc, unsigned int enabled)
 		rtc->uie_rtctimer.node.expires = ktime_add(now, onesec);
 		rtc->uie_rtctimer.period = ktime_set(1, 0);
 		err = rtc_timer_enqueue(rtc, &rtc->uie_rtctimer);
+		if (!err && rtc->ops && rtc->ops->alarm_irq_enable)
+			err = rtc->ops->alarm_irq_enable(rtc->dev.parent, 1);
+		if (err)
+			goto out;
 	} else {
 		rtc_timer_remove(rtc, &rtc->uie_rtctimer);
 	}