PHY polling setup has found a home in the mdio driver. For RTL931x
there still exists a setup sequence for polling type (serdes/mdio)
in the DSA driver. Put it where it belongs.
Signed-off-by: Markus Stockhausen <markus.stockhausen@gmx.de>
Link: https://github.com/openwrt/openwrt/pull/22075
Signed-off-by: Robert Marko <robimarko@gmail.com>