iio: stk3310: Don't return error code in interrupt handler

Interrupt handlers must return one of the irqreturn_t values. Returning a
error code is not supported.

The stk3310 event interrupt handler returns an error code when reading the
flags register fails.

Fix the implementation to always return an irqreturn_t value.

Fixes: 3dd477acbd ("iio: light: Add threshold interrupt support for STK3310")
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Link: https://lore.kernel.org/r/20211024171251.22896-3-lars@metafoo.de
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/light/stk3310.c

@@ -546,9 +546,8 @@ static irqreturn_t stk3310_irq_event_handler(int irq, void *private)
 	mutex_lock(&data->lock);
 	ret = regmap_field_read(data->reg_flag_nf, &dir);
 	if (ret < 0) {
-		dev_err(&data->client->dev, "register read failed\n");
-		mutex_unlock(&data->lock);
-		return ret;
+		dev_err(&data->client->dev, "register read failed: %d\n", ret);
+		goto out;
 	}
 	event = IIO_UNMOD_EVENT_CODE(IIO_PROXIMITY, 1,
 				     IIO_EV_TYPE_THRESH,
@@ -560,6 +559,7 @@ static irqreturn_t stk3310_irq_event_handler(int irq, void *private)
 	ret = regmap_field_write(data->reg_flag_psint, 0);
 	if (ret < 0)
 		dev_err(&data->client->dev, "failed to reset interrupts\n");
+out:
 	mutex_unlock(&data->lock);
 
 	return IRQ_HANDLED;