vdpa/mlx5: Avoid executing set_vq_ready() if device is reset

Avoid executing set_vq_ready() if the device has been reset. In such
case, the features are cleared and cannot be used in conditional
statements. Such reference happens is the function ctrl_vq_idx().

Fixes: 52893733 ("vdpa/mlx5: Add multiqueue support")
Signed-off-by: Eli Cohen <elic@nvidia.com>
Link: https://lore.kernel.org/r/20210909063738.46970-1-elic@nvidia.comSigned-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>

drivers/vdpa/mlx5/net/mlx5_vnet.c

@@ -1714,6 +1714,9 @@ static void mlx5_vdpa_set_vq_ready(struct vdpa_device *vdev, u16 idx, bool ready
 	struct mlx5_vdpa_net *ndev = to_mlx5_vdpa_ndev(mvdev);
 	struct mlx5_vdpa_virtqueue *mvq;
 
+	if (!mvdev->actual_features)
+		return;
+
 	if (!is_index_valid(mvdev, idx))
 		return;