sfxge(4): insert filters for encapsulated packets

sfxge(4): insert filters for encapsulated packets

On Medford, with full-featured firmware running, encapsulated
packets may not be delivered unless filters are inserted for
them, as ordinary filters are not applied to encapsulated
packets. So filters for encapsulated packets need to be
inserted for each class of encapsulated packet. For simplicity,
catch-all filters are always inserted. These may match more
packets than the OS has asked for, but trying to insert more
precise filters increases complexity for little gain.

Submitted by:   Mark Spender <mspender at solarflare.com>
Sponsored by:   Solarflare Communications, Inc.
Differential Revision:  https://reviews.freebsd.org/D18074