Add support for media types from the extended ethernet capabilities fields.

Add support for media types from the extended ethernet capabilities fields.
If none of the regular ethernet capabilities are present, check the extended
capabilities.  Since we only report that the link is active if there's a
detected media type, this isn't just a cosmetic change.

Joerg Streckfuss reported that a gigabit SFP didn't work in a ConnectX-6 Lx,
and tested that this change makes it work.

ok dlg@