arm64: dts: meson-g12a: Add AO-CEC nodes

Amlogic G12A embeds 2 CEC controllers :
- AO-CEC-A the same controller as in GXBB, GXL & GXM SoCs
- AO-CEC-B is a new controller

Note, the two controller can work simultanously since 2 Pads can
handle CEC, thus this SoC can handle 2 distinct CEC busses.

This patch adds the nodes for the AO-CEC-A and AO-CEC-B controllers.

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