iio: adc: ad7091r-base: Use auto cleanup of locks.

Done to reduce boilerplate and simplify code flow by allowing early
returns with the lock automatically released.
Reviewed-by: Nuno Sa <nuno.a@analog.com>
Link: https://lore.kernel.org/r/20240128150537.44592-11-jic23@kernel.orgSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/ad7091r-base.c

@@ -86,28 +86,25 @@ static int ad7091r_read_raw(struct iio_dev *iio_dev,
 	unsigned int read_val;
 	int ret;
 
-	mutex_lock(&st->lock);
+	guard(mutex)(&st->lock);
 
 	switch (m) {
 	case IIO_CHAN_INFO_RAW:
-		if (st->mode != AD7091R_MODE_COMMAND) {
-			ret = -EBUSY;
-			goto unlock;
-		}
+		if (st->mode != AD7091R_MODE_COMMAND)
+			return -EBUSY;
 
 		ret = ad7091r_read_one(iio_dev, chan->channel, &read_val);
 		if (ret)
-			goto unlock;
+			return ret;
 
 		*val = read_val;
-		ret = IIO_VAL_INT;
-		break;
+		return IIO_VAL_INT;
 
 	case IIO_CHAN_INFO_SCALE:
 		if (st->vref) {
 			ret = regulator_get_voltage(st->vref);
 			if (ret < 0)
-				goto unlock;
+				return ret;
 
 			*val = ret / 1000;
 		} else {
@@ -115,17 +112,11 @@ static int ad7091r_read_raw(struct iio_dev *iio_dev,
 		}
 
 		*val2 = chan->scan_type.realbits;
-		ret = IIO_VAL_FRACTIONAL_LOG2;
-		break;
+		return IIO_VAL_FRACTIONAL_LOG2;
 
 	default:
-		ret = -EINVAL;
-		break;
+		return -EINVAL;
 	}
-
-unlock:
-	mutex_unlock(&st->lock);
-	return ret;
 }
 
 static int ad7091r_read_event_config(struct iio_dev *indio_dev,