iio: adc: max1027: Move claim of direct mode up one level and use guard()

Move iio_device_claim_direct_mode() into the read_raw() callback
and use guard() to release a mutex. This enables simpler error
handling via direct returns.

Reviewed-by: Miquel Raynal <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/adc/max1027.c

···
 	int ret;
 	struct max1027_state *st = iio_priv(indio_dev);
 
-	ret = iio_device_claim_direct_mode(indio_dev);
-	if (ret)
-		return ret;
-
 	/* Configure conversion register with the requested chan */
 	st->reg = MAX1027_CONV_REG | MAX1027_CHAN(chan->channel) |
 		  MAX1027_NOSCAN;
···
 	if (ret < 0) {
 		dev_err(&indio_dev->dev,
 			"Failed to configure conversion register\n");
-		goto release;
+		return ret;
 	}
 
 	/*
···
 	 */
 	ret = max1027_wait_eoc(indio_dev);
 	if (ret)
-		goto release;
+		return ret;
 
 	/* Read result */
 	ret = spi_read(st->spi, st->buffer, (chan->type == IIO_TEMP) ? 4 : 2);
-
-release:
-	iio_device_release_direct_mode(indio_dev);
-
 	if (ret < 0)
 		return ret;
 
···
 	int ret = 0;
 	struct max1027_state *st = iio_priv(indio_dev);
 
-	mutex_lock(&st->lock);
+	guard(mutex)(&st->lock);
 
 	switch (mask) {
 	case IIO_CHAN_INFO_RAW:
+		ret = iio_device_claim_direct_mode(indio_dev);
+		if (ret)
+			return ret;
+
 		ret = max1027_read_single_value(indio_dev, chan, val);
-		break;
+		iio_device_release_direct_mode(indio_dev);
+		return ret;
 	case IIO_CHAN_INFO_SCALE:
 		switch (chan->type) {
 		case IIO_TEMP:
 			*val = 1;
 			*val2 = 8;
-			ret = IIO_VAL_FRACTIONAL;
-			break;
+			return IIO_VAL_FRACTIONAL;
 		case IIO_VOLTAGE:
 			*val = 2500;
 			*val2 = chan->scan_type.realbits;
-			ret = IIO_VAL_FRACTIONAL_LOG2;
-			break;
+			return IIO_VAL_FRACTIONAL_LOG2;
 		default:
-			ret = -EINVAL;
-			break;
+			return -EINVAL;
 		}
-		break;
 	default:
-		ret = -EINVAL;
-		break;
+		return -EINVAL;
 	}
-
-	mutex_unlock(&st->lock);
-
-	return ret;
 }
 
 static int max1027_debugfs_reg_access(struct iio_dev *indio_dev,