nfp: update port state in place

Always updating port state in place by overriding values in exiting
pf->eth_tbl makes things easier to manage and allows us to have a
common helper for both full and per-port refresh.

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>