When PHY's are defined on the MDIO bus in the DTS, gigabit support was
being masked out for no apparent reason, pegging all such ports to 10/100.
If gigabit support must be disabled for some reason, there should be a
"max-speed" property in the DTS.
Reported-by: James McKenzie <openwrt@madingley.org>
Signed-off-by: Daniel Gimpelevich <daniel@gimpelevich.san-francisco.ca.us>