net/mlx5: fix crash when setting hairpin queues

net/mlx5: fix crash when setting hairpin queues

If configuring the number of tx/rx queue with rte_eth_dev_configure
to nr_queues + hairpin_nr_queues, and setting tx/rx queues to
nr_queues with rte_eth_tx/rx_queue_setup. But not configuring the
hairpin queues via rte_eth_tx/rx_hairpin_queue_setup.

When starting the netdev, there is a crash because of NULL accessing.

Fixes: cf5516696d77 ("ethdev: add hairpin queue")
Cc: stable@dpdk.org
Signed-off-by: Tonghao Zhang <xiangxia.m.yue@gmail.com>
Acked-by: Ori Kam <orika@mellanox.com>