iio: adc: add missing of_node references to iio_dev

Adding missing indio_dev->dev.of_node references to allow iio consumers
to access the device channels.

Signed-off-by: Matt Ranostay <mranostay@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
diff --git a/drivers/iio/adc/mcp3422.c b/drivers/iio/adc/mcp3422.c
index d1172dc1..254135e 100644
--- a/drivers/iio/adc/mcp3422.c
+++ b/drivers/iio/adc/mcp3422.c
@@ -352,6 +352,7 @@
 	mutex_init(&adc->lock);
 
 	indio_dev->dev.parent = &client->dev;
+	indio_dev->dev.of_node = client->dev.of_node;
 	indio_dev->name = dev_name(&client->dev);
 	indio_dev->modes = INDIO_DIRECT_MODE;
 	indio_dev->info = &mcp3422_info;