hwrng: virtio - unregister device before reset

unregister after reset is clearly wrong - device
can be used while it's reset. There's an attempt to
protect against that using hwrng_removed but it
seems racy since access can be in progress
when the flag is set.

Just unregister, then reset seems simpler and cleaner.
NB: we might be able to drop hwrng_removed in a follow-up patch.
Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/char/hw_random/virtio-rng.c

@@ -179,9 +179,9 @@ static void remove_common(struct virtio_device *vdev)
 	vi->data_avail = 0;
 	vi->data_idx = 0;
 	complete(&vi->have_data);
-	virtio_reset_device(vdev);
 	if (vi->hwrng_register_done)
 		hwrng_unregister(&vi->hwrng);
+	virtio_reset_device(vdev);
 	vdev->config->del_vqs(vdev);
 	ida_simple_remove(&rng_index_ida, vi->index);
 	kfree(vi);