rtc: rv3029: constify rv3029_rtc_ops

Use RTC_FEATURE_ALARM to signal to the core whether alarms are available
instead of changing the global struct rtc_class_ops, allowing to make it
const.
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20210110231752.1418816-15-alexandre.belloni@bootlin.com

drivers/rtc/rtc-rv3029c2.c

@@ -694,10 +694,13 @@ static void rv3029_hwmon_register(struct device *dev, const char *name)
 
 #endif /* CONFIG_RTC_DRV_RV3029_HWMON */
 
-static struct rtc_class_ops rv3029_rtc_ops = {
+static const struct rtc_class_ops rv3029_rtc_ops = {
 	.read_time	= rv3029_read_time,
 	.set_time	= rv3029_set_time,
 	.ioctl		= rv3029_ioctl,
+	.read_alarm	= rv3029_read_alarm,
+	.set_alarm	= rv3029_set_alarm,
+	.alarm_irq_enable = rv3029_alarm_irq_enable,
 };
 
 static int rv3029_probe(struct device *dev, struct regmap *regmap, int irq,
@@ -739,12 +742,10 @@ static int rv3029_probe(struct device *dev, struct regmap *regmap, int irq,
 		if (rc) {
 			dev_warn(dev, "unable to request IRQ, alarms disabled\n");
 			rv3029->irq = 0;
-		} else {
-			rv3029_rtc_ops.read_alarm = rv3029_read_alarm;
-			rv3029_rtc_ops.set_alarm = rv3029_set_alarm;
-			rv3029_rtc_ops.alarm_irq_enable = rv3029_alarm_irq_enable;
 		}
 	}
+	if (!rv3029->irq)
+		clear_bit(RTC_FEATURE_ALARM, rv3029->rtc->features);
 
 	rv3029->rtc->ops = &rv3029_rtc_ops;
 	rv3029->rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;