tg3: Fix 57780 asic rev PCIe link receiver errors

This patch fixes some PCIe link receiver errors by decreasing the internal
electrical idle timeout.

Signed-off-by: Matt Carlson <mcarlson@broadcom.com>
Reviewed-by: Michael Chan <mchan@broadcom.com>
Reviewed-by: Benjamin Li <benli@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>