mlx4_en: Fix cleanup flow on cq activation

In case of mlx4_en_activate_cq() failure, the cleanup
code would go to rx_err and try to disable unactivated rings.

Signed-off-by: Yevgeny Petrilin <yevgenyp@mellanox.co.il>
Signed-off-by: David S. Miller <davem@davemloft.net>