be2net: support ndo_get_phys_port_id()

Add be_get_phys_port_id() function to report physical port id. The port id
should be unique across different be2net devices in the system. We use the
chip serial number along with the physical port number for this.

Signed-off-by: Sriharsha Basavapatna <sriharsha.basavapatna@avagotech.com>
Signed-off-by: David S. Miller <davem@davemloft.net>