Patch from Zwane which fixes a transceiver problem on his 3c905B.

Apparently the 905B's MII status register is saying that it doesn't
need preamble, but the datasheet says that it does.  So add a 905B
override for that in the device table.

This could break other 3c905B's.  I don't know.  There's only one way
to find out.