iio: light apds9960: Add the missing dev.parent

Without this, the iio:deviceX is missing in the /sys/bus/i2c/devices/0-0039
Some userspace tools use this path to identify a specific instance of the
device.
Signed-off-by: Yong Li <sdliyong@gmail.com>
Reviewed-By: Matt Ranostay <mranostay@gmail.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/light/apds9960.c

@@ -1011,6 +1011,7 @@ static int apds9960_probe(struct i2c_client *client,
 
 	iio_device_attach_buffer(indio_dev, buffer);
 
+	indio_dev->dev.parent = &client->dev;
 	indio_dev->info = &apds9960_info;
 	indio_dev->name = APDS9960_DRV_NAME;
 	indio_dev->channels = apds9960_channels;