nfp: remove legacy MAC address lookup

The legacy MAC address lookup doesn't work well with breakout
cables.  We are probably better off picking random addresses
than the wrong ones in the theoretical scenario where management
FW didn't tell us what the port config is.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>