nfp: flower: obtain repr link state only from firmware

Instead of starting up reprs assuming that there is link, only respond
to the link state reported by firmware.

Furthermore, ensure link is down after repr netdevs are created.

Signed-off-by: Dirk van der Merwe <dirk.vandermerwe@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>