In bond 4, when the link goes down and up repeatedly, the bond may get an
unknown speed, and then this port can not work.
The driver notify netif_carrier_on() before update the link state, when the
bond receive carrier on, will query the speed of the port, if the query
operation happens before updating the link state, will get an unknown
speed. So need to notify netif_carrier_on() after update the link state.