rtc: da9063: Handle invalid IRQ from platform_get_irq_byname()

platform_get_irq_byname() might return -errno which later would be
cast to an unsigned int and used in request_irq().
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Tested-by: Adam Thomson <Adam.Thomson.Opensource@diasemi.com>
Link: https://lore.kernel.org/r/20191004150510.6278-1-krzk@kernel.orgSigned-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

drivers/rtc/rtc-da9063.c

@@ -483,6 +483,9 @@ static int da9063_rtc_probe(struct platform_device *pdev)
 		rtc->rtc_dev->uie_unsupported = 1;
 
 	irq_alarm = platform_get_irq_byname(pdev, "ALARM");
+	if (irq_alarm < 0)
+		return irq_alarm;
+
 	ret = devm_request_threaded_irq(&pdev->dev, irq_alarm, NULL,
 					da9063_alarm_event,
 					IRQF_TRIGGER_LOW | IRQF_ONESHOT,