realtek: mdio: setup polling for RTL8261

realtek: mdio: setup polling for RTL8261

Startup of mdio on a RTL8216 based device currently shows the
following warnings.

[1.948608] skip polling setup for unknown PHY 001ccaf3 on port 0
[1.968920] skip polling setup for unknown PHY 001ccaf3 on port 8
[1.989171] skip polling setup for unknown PHY 001ccaf3 on port 16
[2.009704] skip polling setup for unknown PHY 001ccaf3 on port 20
[2.030209] skip polling setup for unknown PHY 001ccaf3 on port 24
[2.052270] realtek-otto-serdes-mdio 1b000000.switchcore:mdio-serdes:
           Realtek SerDes mdio bus initialized, 12 SerDes, 64 pages

Add the phy detection to the mdio bus so that polling setup works.
While we are here sort the phy ids alphabetically.

Signed-off-by: Markus Stockhausen <markus.stockhausen@gmx.de>
Link: https://github.com/openwrt/openwrt/pull/22109
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>