mlx4_en: Fix build warning in mlx4_en_create_rx_ring.

drivers/net/mlx4/en_rx.c: In function ‘mlx4_en_create_rx_ring’:
drivers/net/mlx4/en_rx.c:305: warning: label ‘err_map’ defined but not used
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/mlx4/en_rx.c

@@ -302,8 +302,6 @@ int mlx4_en_create_rx_ring(struct mlx4_en_priv *priv,
 
 	return 0;
 
-err_map:
-	mlx4_en_unmap_buffer(&ring->wqres.buf);
 err_hwq:
 	mlx4_free_hwq_res(mdev->dev, &ring->wqres, ring->buf_size);
 err_ring: