Move CLIP table handling out of TOM and into the base driver.

• Store the clip table in 'struct adapter' instead of in the TOM softc.
• Init the clip table during attach and teardown during detach.
• While here, add a dev.<nexus>.<unit>.misc.clip sysctl to dump the CLIP table.

This does mean that we update the clip table even if TOE is not enabled,
but non-TOE things need the CLIP table anyway.

Reviewed by: np, Krishnamraju Eraparaju @ Chelsio
Sponsored by: Chelsio Communications
Differential Revision: https://reviews.freebsd.org/D18010