Onboard AR8035 PHY supports 1000Base-T operation, but onboard
Ethernet magnetics do not. Reduce advertised link speeds to 100Mbps and
lower.
Signed-off-by: Lech Perczak <lech.perczak@gmail.com>
(cherry picked from commit d406777fb14c84e82f51bab059631af70cf6d5c9)