sfxge: rename common hunt PHY methods to ef10 and use for Medford

Leaving BIST methods for now as, though the Medford bootrom now has lots
of BIST support, production firmware doesn't appear to have been updated
yet.

Submitted by: Mark Spender <mspender at solarflare.com>
Reviewed by: gnn
Sponsored by: Solarflare Communications, Inc.
MFC after: 2 days
Differential Revision: https://reviews.freebsd.org/D4949