iio: accel: mma9551: Check gpiod_to_irq return value

The return value of gpiod_to_irq should be checked before giving
it to devm_request_threaded_irq in order to not pass an error
code in case it fails.

Signed-off-by: Roberta Dobrescu <[e-mail]>
Reviewed-by: Vlad Dogaru <[e-mail]>
Acked-by: Uwe Kleine-König <[e-mail]>
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/accel/mma9551.c

···
 			return PTR_ERR(gpio);
 		}
 
-		data->irqs[i] = gpiod_to_irq(gpio);
+		ret = gpiod_to_irq(gpio);
+		if (ret < 0)
+			return ret;
+
+		data->irqs[i] = ret;
 		ret = devm_request_threaded_irq(dev, data->irqs[i],
 				NULL, mma9551_event_handler,
 				IRQF_TRIGGER_RISING | IRQF_ONESHOT,