rtc: sysfs: check features instead of ops

Test RTC_FEATURE_ALARM instead of relying on .set_alarm to know whether
alarms are available.

Signed-off-by: Alexandre Belloni <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

drivers/rtc/sysfs.c

···
 	if (!device_can_wakeup(rtc->dev.parent))
 		return false;
 
-	return rtc->ops->set_alarm != NULL;
+	return !!test_bit(RTC_FEATURE_ALARM, rtc->features);
 }
 
 static umode_t rtc_attr_is_visible(struct kobject *kobj,