iio: adc: stm32-dfsdm: fix data type

Fix the data type as DFSDM raw output is complements 2,
24bits left aligned in a 32-bit register.
This change does not affect AUDIO path
- Set data as signed for IIO (as for AUDIO)
- Set 8 bit right shift for IIO.
The 8 LSBs bits of data contains channel info and are masked.
Signed-off-by: Olivier Moysan <olivier.moysan@st.com>
Fixes: e2e6771c ("IIO: ADC: add STM32 DFSDM sigma delta ADC support")
Acked-by: Fabrice Gasnier <fabrice.gasnier@st.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/stm32-dfsdm-adc.c

@@ -1365,11 +1365,11 @@ static int stm32_dfsdm_adc_chan_init_one(struct iio_dev *indio_dev,
 					BIT(IIO_CHAN_INFO_SAMP_FREQ);
 
 	if (adc->dev_data->type == DFSDM_AUDIO) {
-		ch->scan_type.sign = 's';
 		ch->ext_info = dfsdm_adc_audio_ext_info;
 	} else {
-		ch->scan_type.sign = 'u';
+		ch->scan_type.shift = 8;
 	}
+	ch->scan_type.sign = 's';
 	ch->scan_type.realbits = 24;
 	ch->scan_type.storagebits = 32;