IIO: ADC: stm32-dfsdm: avoid unused-variable warning

Building with CONFIG_OF disabled produces a compiler warning:

drivers/iio/adc/stm32-dfsdm-core.c: In function 'stm32_dfsdm_probe':
drivers/iio/adc/stm32-dfsdm-core.c:245:22: error: unused variable 'pnode' [-Werror=unused-variable]

This removes the variable and open-codes it in the only place
it gets used to avoid that warning.

Fixes: bed73904e76f ("IIO: ADC: add stm32 DFSDM core support")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Mark Brown <broonie@kernel.org>

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

@@ -242,7 +242,6 @@ MODULE_DEVICE_TABLE(of, stm32_dfsdm_of_match);
 static int stm32_dfsdm_probe(struct platform_device *pdev)
 {
 	struct dfsdm_priv *priv;
-	struct device_node *pnode = pdev->dev.of_node;
 	const struct of_device_id *of_id;
 	const struct stm32_dfsdm_dev_data *dev_data;
 	struct stm32_dfsdm *dfsdm;
@@ -254,7 +253,7 @@ static int stm32_dfsdm_probe(struct platform_device *pdev)
 
 	priv->pdev = pdev;
 
-	of_id = of_match_node(stm32_dfsdm_of_match, pnode);
+	of_id = of_match_node(stm32_dfsdm_of_match, pdev->dev.of_node);
 	if (!of_id->data) {
 		dev_err(&pdev->dev, "Data associated to device is missing\n");
 		return -EINVAL;