realtek: add phy-handle for Zyxel GS1900-10HP SFP slots
Align GS1900-10HP dts with other realtek devices to reduce the risk of device
specific regressions with the upcoming driver cleanup/rewrite.
Signed-off-by: Bjørn Mork <[email protected]>
Link: https://github.com/openwrt/openwrt/pull/20228
Signed-off-by: Robert Marko <[email protected]>