MFC r276959:

MFC r276959:
cxgb: replace r273280 with a more comprehensive fix.

Poll for link state when the link is down, even for interrupt capable
PHYs.

Allow PHYs to report a dubious "partial" link.  If this state is seen 3
consecutive times (each check is ~1s apart) then reset the PHY.  This is
a workaround for a situation where repeatedly toggling the link from the
peer gets the AEL2005 PHY into a state where it never establishes a PCS
block lock even when everything is in order.

git-svn-id: svn://svn.freebsd.org/base/stable/10@277343 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f