There are still a lot of mdio functions scattered around the code.
Move the RTL838x serdes helpers closer to the bus, add the proper
prefix and simplify the functions.
Signed-off-by: Markus Stockhausen <markus.stockhausen@gmx.de>
Link: https://github.com/openwrt/openwrt/pull/18847
Signed-off-by: Robert Marko <robimarko@gmail.com>