realtek: dsa,pcs: rtl931x: let PCS driver setup SerDes

realtek: dsa,pcs: rtl931x: let PCS driver setup SerDes

Remove SerDes initialization/configuration calls from the DSA driver in
'rtl931x_phylink_mac_config' and let our PCS driver setup the SerDes now
that the driver is able to do that.

pcs_config of the PCS driver is automatically called by phylink, thus
there's no need to call it on our own.

Note that in rtl931x_phylink_mac_config the MAC is enabled before
pcs_config is called. While this seems to work, it isn't good and needs
to be fixed.

Signed-off-by: Jonas Jelonek <jelonek.jonas@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/20369
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>