vdpa/mlx5: Fix failure to bring link up

Set VIRTIO_NET_S_LINK_UP in config status to allow the get the bring the
net device's link up.

Fixes: 1a86b377 ("vdpa/mlx5: Add VDPA driver for supported mlx5 devices")
Signed-off-by: NEli Cohen <elic@nvidia.com>
Link: https://lore.kernel.org/r/20200917121540.GA98184@mtl-vdi-166.wap.labs.mlnxSigned-off-by: NMichael S. Tsirkin <mst@redhat.com>
Acked-by: NJason Wang <jasowang@redhat.com>

drivers/vdpa/mlx5/net/mlx5_vnet.c

@@ -1541,6 +1541,7 @@ static int mlx5_vdpa_set_features(struct vdpa_device *vdev, u64 features)
 
 	ndev->mvdev.actual_features = features & ndev->mvdev.mlx_features;
 	ndev->config.mtu = cpu_to_mlx5vdpa16(mvdev, ndev->mtu);
+	ndev->config.status |= cpu_to_mlx5vdpa16(mvdev, VIRTIO_NET_S_LINK_UP);
 	return err;
 }