GMII support for miibus(4)

[Sepherosa Ziehau]

Hi all,

Following patch brings in updates (mainly more standard conforming
GMII support) for miibus(4) from NetBSD/OpenBSD:
http://leaf.dragonflybsd.org/~sephe/mii.diff
This should apply cleanly to both HEAD and 1.6 branch

I have managed to test some of the PHY modules:
acphy, brgphy, e1000phy, exphy, inphy, rgephy, rlphy, ruephy and ukphy
!! NOTE:
1) nvphy is gone, ukphy now has generic GMII support
2) If you have _no_ physical access to the box, on which you are going
to test the patch, please DO NOT try applying the patch, since this
patch may make you loss connection to your box.
Please review/test it (again, test the patch only if you have physical
access to your testing box)
If no problem or objection comes, I will commit it two weeks later.

Best Regards,
sephe
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