cxgb4vf: Call netif_carrier_off properly in pci_probe

netif_carrier_off() should be called only after register_netdev().

Signed-off-by: Arjun Vynipadath <arjun@chelsio.com>
Signed-off-by: Vishal Kulkarni <vishal@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>