net: phylink: explicitly invalidate link_state members in mac_config

Explicitly invalidate the phylink_link_state structure members in
mac_config that do not contain reliable information for this function,
thereby preventing their future incorrect use.

Reviewed-by: Daniel Golle <daniel@makrotopia.org>
Tested-by: Daniel Golle <daniel@makrotopia.org>
Tested-by: Frank Wunderlich <frank-w@public-files.de>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>