vhost: move -net specific code out

Zerocopy handling code is vhost-net specific.
Move it from vhost.c/vhost.h out to net.c

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/vhost/tcm_vhost.c

@@ -895,6 +895,7 @@ static int vhost_scsi_release(struct inode *inode, struct file *f)
 		vhost_scsi_clear_endpoint(s, &backend);
 	}
 
+	vhost_dev_stop(&s->dev);
 	vhost_dev_cleanup(&s->dev, false);
 	kfree(s);
 	return 0;