mlx4_en: Removing reserve vectors

Fixed a bug where ring size change caused insufficient memory
upon driver restart due to unreleased EQs.

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