If we call `netif_register()` before we can be sure that the interface can be configured, a 'zombie' interface remains in the list, causing all kinds of trouble down the line. Only call `netif_register()` if `init()` was successful.
If we call `netif_register()` before we can be sure that the interface can be configured, a 'zombie' interface remains in the list, causing all kinds of trouble down the line. Only call `netif_register()` if `init()` was successful.