iio: adc: stm32-dfsdm: handle label as an optional property

The label property is defined as optional in the DFSDM binding.
Parse the label property only when it is defined in the device tree.

Fixes: 3208fa0 ("iio: adc: stm32-dfsdm: adopt generic channels bindings")
Signed-off-by: Olivier Moysan <olivier.moysan@foss.st.com>
Link: https://patch.msgid.link/20241114102459.2497178-1-olivier.moysan@foss.st.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Author: Olivier Moysan

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

@@ -691,11 +691,14 @@ static int stm32_dfsdm_generic_channel_parse_of(struct stm32_dfsdm *dfsdm,
 		return -EINVAL;
 	}
 
-	ret = fwnode_property_read_string(node, "label", &ch->datasheet_name);
-	if (ret < 0) {
-		dev_err(&indio_dev->dev,
-			" Error parsing 'label' for idx %d\n", ch->channel);
-		return ret;
+	if (fwnode_property_present(node, "label")) {
+		/* label is optional */
+		ret = fwnode_property_read_string(node, "label", &ch->datasheet_name);
+		if (ret < 0) {
+			dev_err(&indio_dev->dev,
+				" Error parsing 'label' for idx %d\n", ch->channel);
+			return ret;
+		}
 	}
 
 	df_ch =  &dfsdm->ch_list[ch->channel];