net/mlx5: Don't perform lookup after already known sec_path

There is no need to perform extra lookup in order to get already
known sec_path that was set a couple of lines above. Simply reuse it.

Reviewed-by: Raed Salem <raeds@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>