- Provide lagg_proto_attach(), lagg_proto_detach().
- Make detach a protocol method in lagg_protos.
- Simplify code to lookup protocols.

Sponsored by:	Netflix
Sponsored by:	Nginx, Inc.


git-svn-id: svn+ssh://svn.freebsd.org/base/head@272170 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f
Add smsc(4) to the list of drivers use the miibus interface.

X-MFC with:	r272165
Sponsored by:	Nginx, Inc.


git-svn-id: svn+ssh://svn.freebsd.org/base/head@272171 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f