nfp: call netif_carrier_off() during init

Netdevs default to carrier on, we should call netif_carrier_off()
during initialization since we handle carrier state changes in the
driver.

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