vhost-vdpa: remove the unnecessary check in vhost_vdpa_add()

The VhostVDPAState is just allocated by qemu_new_net_client() via
g_malloc0() in net_vhost_vdpa_init(). So s->vhost_net is NULL for
sure, let's remove this unnecessary check in vhost_vdpa_add().

Signed-off-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20210903091031.47303-7-jasowang@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

net/vhost-vdpa.c

@@ -111,10 +111,6 @@ static int vhost_vdpa_add(NetClientState *ncs, void *be)
         error_report("failed to init vhost_net for queue");
         goto err;
     }
-    if (s->vhost_net) {
-        vhost_net_cleanup(s->vhost_net);
-        g_free(s->vhost_net);
-    }
     s->vhost_net = net;
     ret = vhost_vdpa_net_check_device_id(net);
     if (ret) {