82599ES support

[Lyndon Nerenberg]

We're looking to buy some 10-gig SFP+ boards, and are eyeing up 
Supermicro's 2-port boards (listed as the 'Intel 82599ES - AOC-STGN-i2S').

ix(4) doesn't list the ES variant of the chip, and a quick grep through 
the driver source doesn't mention it explicitly, either.  Are any of you 
running this board under >= 6.0 ?

(We need to buy these boards as part of a single lease, so I'm constrained 
on what's available.  Otherwise I'd just buy some X520s.)

--lyndon