PCH_GbE : Fixed the issue of collision detection

The collision detection setting was invalid.
When collision occurred, because data was not resent,
there was an issue to which a transmitting throughput falls.

This patch enables the collision detection.

Signed-off-by: Toshiharu Okada <toshiharu-linux@dsn.okisemi.com>
Signed-off-by: David S. Miller <davem@davemloft.net>