net/mlx5: fix double free on error handling
net/mlx5: fix double free on error handling

When attr_ctx is NULL it will attempt to free the list of devices twice.
Avoid double freeing the list by directly going to error handling.

Fixes: 771fa900b73a ("mlx5: introduce new driver for Mellanox ConnectX-4 adapters")
Cc: stable@dpdk.org

Signed-off-by: Raslan Darawsheh <18fd192a829ab99382a9c480ddb6085edf3e8489@mellanox.com>
Acked-by: Yongseok Koh <76b37c91816d73ef9cf709e3e83a68f2d162f1e2@mellanox.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk