net/mlx4_core: Looking for promiscuous entries on the correct port

The search for promisc entries was always done on the first port,
While the addition is done on the correct port.
This lead to resource leackage of promisc entries on the second
port and brought to a state where we could no longer enter to
promiscuous mode after enough iterations of "ifconfig promisc"
on the second port.
Fix that by using the correct port when searching.

Reported-by: Marcelo Ricardo Leitner <mleitner@redhat.com>
Signed-off-by: Aviad Yehezkel <aviadye@mellanox.com>
Signed-off-by: Yevgeny Petrilin <yevgenyp@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>