iio: adc: ad7791: Factor out core of ad7791_write_raw() to simplify error handling

Factor out everything under the direct mode claim allowing direct returns
in error paths.

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

drivers/iio/adc/ad7791.c

···
 	return -EINVAL;
 }
 
-static int ad7791_write_raw(struct iio_dev *indio_dev,
+static int __ad7791_write_raw(struct iio_dev *indio_dev,
 	struct iio_chan_spec const *chan, int val, int val2, long mask)
 {
 	struct ad7791_state *st = iio_priv(indio_dev);
-	int ret, i;
-
-	ret = iio_device_claim_direct_mode(indio_dev);
-	if (ret)
-		return ret;
+	int i;
 
 	switch (mask) {
 	case IIO_CHAN_INFO_SAMP_FREQ:
···
 				break;
 		}
 
-		if (i == ARRAY_SIZE(ad7791_sample_freq_avail)) {
-			ret = -EINVAL;
-			break;
-		}
+		if (i == ARRAY_SIZE(ad7791_sample_freq_avail))
+			return -EINVAL;
 
 		st->filter &= ~AD7791_FILTER_RATE_MASK;
 		st->filter |= i;
 		ad_sd_write_reg(&st->sd, AD7791_REG_FILTER,
 				sizeof(st->filter),
 				st->filter);
-		break;
+		return 0;
 	default:
-		ret = -EINVAL;
+		return -EINVAL;
 	}
+}
+
+static int ad7791_write_raw(struct iio_dev *indio_dev,
+	struct iio_chan_spec const *chan, int val, int val2, long mask)
+{
+	int ret;
+
+	ret = iio_device_claim_direct_mode(indio_dev);
+	if (ret)
+		return ret;
+
+	ret = __ad7791_write_raw(indio_dev, chan, val, val2, mask);
 
 	iio_device_release_direct_mode(indio_dev);
 	return ret;