There's no measurable performance impact1 of leaving an unused ng_ether node attached to ethernet interfaces, so don't waste time trying to ensure we only attach to interfaces where we expect to use netgraph.
[1] Tested with if_bridge, no difference observed passing ~9Mpps and routing, also no diffference observed at ~29Mpps.
Do not detach ng_ether from physical interfaces
There's no measurable performance impact1 of leaving an unused ng_ether
node attached to ethernet interfaces, so don't waste time trying to
ensure we only attach to interfaces where we expect to use netgraph.
[1] Tested with if_bridge, no difference observed passing ~9Mpps and
routing, also no diffference observed at ~29Mpps.
Redmine: #7067