staging: iio: call iio_device_unregister() in max517_remove()

Reported-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Peter Meerwald <pmeerw@pmeerw.net>
Acked-by: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/iio/dac/max517.c

@@ -264,6 +264,7 @@ static int max517_probe(struct i2c_client *client,
 
 static int max517_remove(struct i2c_client *client)
 {
+	iio_device_unregister(i2c_get_clientdata(client));
 	iio_device_free(i2c_get_clientdata(client));
 
 	return 0;