pch_gbe: fixed the issue which receives an unnecessary packet.

This patch fixed the issue which receives an unnecessary packet before link

When using PHY of GMII, an unnecessary packet is received,
And it becomes impossible to receive a packet after link up.

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