MFC: r217415

MFC: r217415

- Allow IFM_FLAG0 to be set indicating that auto-negotiation with manual
  configuration, which is used to work around issues with certain setups
  (see r161237) by default, should not be triggered as it may in turn
  cause harm in some edge cases.
- Even after masking the media with IFM_GMASK the result may have bits
  besides the duplex ones set so just comparing it with IFM_FDX may lead
  to false negatives.
- Announce PAUSE support also for manually selected 1000BASE-T, but for
  all manually selected media types only in full-duplex mode. Announce
  asymmetric PAUSE support only for manually selected 1000BASE-T.
- Simplify setting the manual configuration bits to only once after we
  have figured them all out. This also means we no longer unnecessarily
  update the hardware along the road.
- Remove a stale comment.

Reviewed by:	yongari (plus additional testing)
Approved by:	re (bz)

git-svn-id: svn://svn.freebsd.org/base/releng/8.2@217666 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f