dt-bindings: clock: amlogic, gxbb-aoclkc: Update bindings

On the first revision of the bindings, only the gates + resets were known
in the AO Clock HW, but more registers used to configures AO clock are known
to be spread among the AO register space.
This patch adds a parent node for the entire system control zone for the AO
domain then moves the clock controller as a subnode of the system control
node.

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