realtek: mdio: rename main mdio bus

realtek: mdio: rename main mdio bus

Looking at the Realtek mdio busses there are curently the following

root@OpenWrt:~# mdio
1b000000.switchcore:mdio-controller-mii
fixed-0
realtek-aux-mdio
realtek-serdes-mdio
rtldsa_mdio-0

The main mdio bus for the phys is named after the dts node it belongs
to (1b000000.switchcore:mdio-controller-mii). As it is attached to the
controller node it is even more confusing.

Align the naming to the other busses and use "realtek-mdio".

Signed-off-by: Markus Stockhausen <markus.stockhausen@gmx.de>
Link: https://github.com/openwrt/openwrt/pull/21702
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>