arm64: dts: amlogic: gxl: use gxl mdio multiplexer

arm64: dts: amlogic: gxl: use gxl mdio multiplexer

So the far, GXL SoCs were using the generic mmio register based mdio
multiplexer. This properly sets one of the glue register but the SoC
actually has 3 of those registers.

One of them sets the ID under which the internal phy will advertise
itself. If nothing sets this register before linux boots (like u-boot), the
internal phy path is broken.

To address this problem, a dedicated MDIO mux driver has been
introduced. Switch to this new driver.

Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Link: https://lore.kernel.org/r/20230306151354.132973-1-jbrunet@baylibre.com
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>