net: phylink: ensure inband AN works correctly

Do not update the link interface mode while the link is down to avoid
spurious link interface changes.

Always call mac_config if we have a PHY to propagate the pause mode
settings to the MAC.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>