Fix for kern/20700 - was: wm(4) won't negotiate 1000-base-T with Cisco switches and won't operate with manual settings

[buhrow%lothlorien.nfbcal.org@localhost (Brian Buhrow)]

        Hello.  It turns out that this problem is the same as kern/20700.
I've written a patch which addresses this bug and submitted it to the pr.
If no one objects, I'll commit this patch in a few days and request a
pullup to the 5.x branch.  If there are objections, I'm happy to discuss
and/or incorporate a better fix.  This fix works quite well in my case.
-thanks
-Brian