realtek: phy: cleanup RTL8214C configuration

realtek: phy: cleanup RTL8214C configuration

RTL8214C configuration is currently useless.

- It uses register 29 (write only companion of ext. page register 30)
- "configuration" only reads registers 2/3 and writes a message
- "configuration" is run during probing

Drop the useless coding. As this was the last consumer drop register
29 define too.

Signed-off-by: Markus Stockhausen <markus.stockhausen@gmx.de>
Link: https://github.com/openwrt/openwrt/pull/21716
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>