tulip/de2104x: don't report different speeds depending on port type

Initial driver reported different speeds depending on the port being
used. This advertises the speed to be 10Mbps in any case, which is
what it actually is on the wire.

Signed-off-by: David Decotigny <decot@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>