iio: adc: ad7192: Fix null ad7192_state pointer access

Pointer to indio_dev structure is obtained via spi_get_drvdata() at
the beginning of function ad7192_setup(), but the spi->dev->driver_data
member is not initialized, hence a NULL pointer is returned.

Fix by changing ad7192_setup() signature to take pointer to struct
iio_dev, and get ad7192_state pointer via st = iio_priv(indio_dev);

Fixes: bd5dcdeb ("iio: adc: ad7192: convert to device-managed functions")
Signed-off-by: Fabrizio Lamarque <fl.scratchpad@gmail.com>
Reviewed-by: Nuno Sa <nuno.sa@analog.com>
Cc: <Stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20230530075311.400686-2-fl.scratchpad@gmail.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/ad7192.c

@@ -380,9 +380,9 @@ static int ad7192_of_clock_select(struct ad7192_state *st)
 	return clock_sel;
 }
 
-static int ad7192_setup(struct ad7192_state *st, struct device_node *np)
+static int ad7192_setup(struct iio_dev *indio_dev, struct device_node *np)
 {
-	struct iio_dev *indio_dev = spi_get_drvdata(st->sd.spi);
+	struct ad7192_state *st = iio_priv(indio_dev);
 	bool rej60_en, refin2_en;
 	bool buf_en, bipolar, burnout_curr_en;
 	unsigned long long scale_uv;
@@ -1069,7 +1069,7 @@ static int ad7192_probe(struct spi_device *spi)
 		}
 	}
 
-	ret = ad7192_setup(st, spi->dev.of_node);
+	ret = ad7192_setup(indio_dev, spi->dev.of_node);
 	if (ret)
 		return ret;