Tulip: don't initialize SBE xT3E3 WAN ports.

SBE 2T3E3 cards use DECchips 21143 but they need a different driver.
Don't even try to use a normal tulip driver with them.

Signed-off-by: Krzysztof Hałasa <khc@pm.waw.pl>
Signed-off-by: David S. Miller <davem@davemloft.net>