arm64: dts: meson-axg: s400: Enable PHY interrupt

Now that the GPIO controller has been enabled also on AXG we can hook up
the GPIO interrupt for the PHY.

Tested-by: Jerome Brunet <jbrunet@baylibre.com>
Signed-off-by: Carlo Caione <ccaione@baylibre.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>