Revert "vhost-net: do not crash if backend is not present"

Now that get_vhost_net() returns non-null after a successful
vhost_net_init(), we no longer need to check this case.

This reverts commit ecd34898596c60f79886061618dd7e01001113ad.
Signed-off-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

hw/net/vhost_net.c

@@ -429,15 +429,10 @@ VHostNetState *get_vhost_net(NetClientState *nc)
 int vhost_set_vring_enable(NetClientState *nc, int enable)
 {
     VHostNetState *net = get_vhost_net(nc);
-    const VhostOps *vhost_ops;
+    const VhostOps *vhost_ops = net->dev.vhost_ops;
 
     nc->vring_enable = enable;
 
-    if (!net) {
-        return 0;
-    }
-
-    vhost_ops = net->dev.vhost_ops;
     if (vhost_ops->vhost_set_vring_enable) {
         return vhost_ops->vhost_set_vring_enable(&net->dev, enable);
     }