usbnet: Set parent device early for netdev_printk()

netdev_printk() follows the net_device's parent device pointer, so
we must set that earlier than we previously did.

Reported-by: Luís Picciochi Oliveira <pitxyoki@gmail.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>