net: dsa: Make PHYLINK related function static again

Commit 77373d49

 ("net: dsa: Move the phylink driver calls into
port.c") moved and exported a bunch of symbols, but they are not used
outside of net/dsa/port.c at the moment, so no reason to export them.

Reported-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Vivien Didelot <vivien.didelot@gmail.com>
Acked-by: Russell King <rmk+kernel@armlinux.org.uk>
Acked-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>