realtek: mdio: derive phy smi-bus from parent node

realtek: mdio: derive phy smi-bus from parent node

The dts for RTL93xx devices has duplicate data about the
smi bus of a phy node. The parent node declares the number
of the bus and the realtek,smi-address attribute does the
same.

Remove the bus part from the realtek,smi-address attribute
and lookup the bus from the parent node. While we are here
remove all realtek,smi-address attributes where phy id
matches the bus address. The driver will use that as a
fallback.

Signed-off-by: Markus Stockhausen <markus.stockhausen@gmx.de>
Link: https://github.com/openwrt/openwrt/pull/21438
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>