rtc: pl031: make interrupt optional

On some platforms, the interrupt for the PL031 is optional.  Avoid
trying to claim the interrupt if it's not specified.
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>

drivers/rtc/rtc-pl031.c

@@ -308,6 +308,7 @@ static int pl031_remove(struct amba_device *adev)
 
 	dev_pm_clear_wake_irq(&adev->dev);
 	device_init_wakeup(&adev->dev, false);
+	if (adev->irq[0])
 		free_irq(adev->irq[0], ldata);
 	rtc_device_unregister(ldata->rtc);
 	amba_release_regions(adev);
@@ -389,12 +390,13 @@ static int pl031_probe(struct amba_device *adev, const struct amba_id *id)
 		goto out;
 	}
 
-	if (request_irq(adev->irq[0], pl031_interrupt,
-			vendor->irqflags, "rtc-pl031", ldata)) {
-		ret = -EIO;
+	if (adev->irq[0]) {
+		ret = request_irq(adev->irq[0], pl031_interrupt,
+				  vendor->irqflags, "rtc-pl031", ldata);
+		if (ret)
 			goto out_no_irq;
-	}
 		dev_pm_set_wake_irq(&adev->dev, adev->irq[0]);
+	}
 	return 0;
 
 out_no_irq: