Linux does not do that in register_netdev() either. Some drivers set the
carrier flags on attach and never reenable it (as seen with rndis_host).
Consequently, the usbnet driver refuses to receive data as it checks the
carrier state before enqueuing new SKBs to its receive queue.
Apart from rndis_host, this change was tested with an ax88179_178a
device which worked as expected.