net: dsa: sja1105: call PCS config/link_up via pcs_ops structure

Call the PCS operations through the ops structure, which avoids needing
to export xpcs internal functions.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Link: https://patch.msgid.link/E1svfMf-005ZId-Mx@rmk-PC.armlinux.org.uk


Signed-off-by: Jakub Kicinski <kuba@kernel.org>