Add function to get the device physical port of the lag slave.
Signed-off-by: NMaor Gottlieb <maorg@mellanox.com>
Reviewed-by: NLeon Romanovsky <leonro@mellanox.com>
Acked-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NSaeed Mahameed <saeedm@mellanox.com>