The RTL8224 used by Plasma Cloud PSX8/PSX10 is not using USXGMII but
USXGMII 10G-QXGMII mode. The correct phy-mode string for this is
"10g-qxgmii".
Signed-off-by: Sven Eckelmann <se@simonwunderlich.de>
Link: https://github.com/openwrt/openwrt/pull/20239
Signed-off-by: Robert Marko <robimarko@gmail.com>