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: NLinus Walleij <linus.walleij@linaro.org>
Signed-off-by: NRussell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: NAlexandre Belloni <alexandre.belloni@free-electrons.com>

drivers/rtc/rtc-pl031.c

@@ -308,7 +308,8 @@ static int pl031_remove(struct amba_device *adev)
 
 	dev_pm_clear_wake_irq(&adev->dev);
 	device_init_wakeup(&adev->dev, false);
-	free_irq(adev->irq[0], ldata);
+	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;
-		goto out_no_irq;
+	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]);
 	}
-	dev_pm_set_wake_irq(&adev->dev, adev->irq[0]);
 	return 0;
 
 out_no_irq: