mii: add Vitesse/Microsemi VSC8514

The VSC8514 Quad-Port 10/100/1000BASE-T PHY seems to match the handling
for the VSC8504 (for the little we support of what we could) and while
it works with our generic ukphy add it as vscphy for porper display of
names in the system message buffer and the like (or in case we decide
to implement some extra features).

Tested on: Ten64
MFC after: 3 days