IB/mlx5: Port status track LAG master, when LAG is active

When LAG is active, port up/down events should be triggered
by tracking the LAG master, and not one of the two slave
netdevs.

In the same manner, ib_query_port() should return the details
of the LAG master.

Signed-off-by: Aviv Heller <avivh@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>