rtc: isl1208: do not advertise update interrupt feature if no interrupt specified

If an ISL1208 device does not have an interrupt line routed, the feature
shouldn't be advertised (it is by default in rtc core) or it'll confuse
userspace requesting that feature (such as hwclock from util-linux).
Signed-off-by: Quentin Schulz <quentin.schulz@theobroma-systems.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20220523145320.123713-1-foss+kernel@0leil.net

drivers/rtc/rtc-isl1208.c

@@ -880,10 +880,14 @@ isl1208_probe(struct i2c_client *client, const struct i2c_device_id *id)
 	if (rc)
 		return rc;
 
-	if (client->irq > 0)
+	if (client->irq > 0) {
 		rc = isl1208_setup_irq(client, client->irq);
-	if (rc)
-		return rc;
+		if (rc)
+			return rc;
+
+	} else {
+		clear_bit(RTC_FEATURE_UPDATE_INTERRUPT, isl1208->rtc->features);
+	}
 
 	if (evdet_irq > 0 && evdet_irq != client->irq)
 		rc = isl1208_setup_irq(client, evdet_irq);