nfp: report port type in ethtool

Service process firmware provides us with information about media
and interface (SFP module) plugged in, translate that to Linux's
PORT_* defines and report via ethtool.

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