iio: st_sensors: print error when failing to get IRQ

Print a proper error message if we're missing the trigger
IRQ.
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/common/st_sensors/st_sensors_trigger.c

@@ -37,8 +37,10 @@ int st_sensors_allocate_trigger(struct iio_dev *indio_dev,
 			IRQF_TRIGGER_RISING,
 			sdata->trig->name,
 			sdata->trig);
-	if (err)
+	if (err) {
+		dev_err(&indio_dev->dev, "failed to request trigger IRQ.\n");
 		goto request_irq_error;
+	}
 
 	iio_trigger_set_drvdata(sdata->trig, indio_dev);
 	sdata->trig->ops = trigger_ops;