ticular, these overzealous register writes can cause misdetection
problems.

Update to do the following once (not once per port) at boot:
	read 16-bit PCS
	if needs changing,
		write 16-bit PCS

And thereafter, we only perform a 'read 16-bit PCS' per port.

This should eliminate all PCS writes in many cases, and be more friendly
in the cases where we do need to enable ports.

Signed-off-by: Jeff Garzik <jeff@garzik.org>