dt-bindings: soc: amlogic,meson-gx-hhi-sysctrl: add example covering meson-axg-hhi-sysctrl

Add a third example covering the meson-axg-hhi-sysctrl variant and more
importantly the phy subnode.

Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20231124-amlogic-v6-4-upstream-dsi-ccf-vim3-v9-2-95256ed139e6@linaro.org


Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>