ARM64: dts: meson-gx: update AO clkc to new bindings

The AO clkc needs to be updated to new bindings with an system control parent
node and moving the clkc node as subnode.

Also adds the SoC specific compatible following the bindings requirements.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>