realtek: dsa,pcs: rtl930x: let PCS driver setup SerDes

realtek: dsa,pcs: rtl930x: let PCS driver setup SerDes

Remove SerDes initialization/configuration calls from the DSA driver in
'rtl93xx_phylink_mac_config' and let our PCS driver setup the SerDes now
that the driver is able to do that.

Adjust some details in rtl93xx_phylink_mac_config to ensure the MAC is
properly disabled MAC before configuring the SerDes. This was done
within the SerDes code before.

Signed-off-by: Jonas Jelonek <[email protected]>
Link: https://github.com/openwrt/openwrt/pull/20539
Signed-off-by: Robert Marko <[email protected]>