net/mlx4_en: Release QP range in free_resources

Add a missing resource release in ring cleanup.
Not doing this leaves a range of QPs that are being reserved,
and no one can use them.

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