Major changes:

- Add i219/i219(2) hardware support. (Found on Skylake generation and newer
  chipsets.)
  - Further to the last Skylake support diff, this one also includes support for
    the Lewisburg chipset (i219(3)).

- Add a workaround to an igb hardware errata.
  All 1G server products need to have IPv6 extension header parsing turned off.
  This should be listed in the specification updates for current 1G server
  products, e.g. for i350 it's errata #37 in this document:
  http://www.intel.com/content/dam/www/public/us/en/documents/specification-updates/ethernet-controller-i350-spec-update.pdf

- Avoton (i354) PHY errata workaround added

And a bunch of minor fixes, as well as #defines for things that the current
em(4)/igb(4) drivers don't implement.

Differential Revision: https://reviews.freebsd.org/D3162
Reviewed by: sbruno, marius, gnn
Approved by: gnn
MFC after: 2 weeks
Sponsored by: Intel Corporation