move virtballoon_remove to .devexit.text

The function virtballoon_remove is used only wrapped by __devexit_p so
define it using __devexit.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

drivers/virtio/virtio_balloon.c

@@ -247,7 +247,7 @@ out:
 	return err;
 }
 
-static void virtballoon_remove(struct virtio_device *vdev)
+static void __devexit virtballoon_remove(struct virtio_device *vdev)
 {
 	struct virtio_balloon *vb = vdev->priv;