ethernet: remove callback boilerplate from EthernetNetworkFactory

Now that everything uses EthernetCallback, there is no need for the
boilerplate code in EthernetNetworkFactory anymore.

The next step will be to pull the callbacks out of
EthernetNetworkFactory entirely.

Bug: 225317892
Test: atest EthernetNetworkFactory
Change-Id: I4958df658f7d5852660a5c03a8c9220532e42d3c
1 file changed