media: dt-bindings: media: Add Amlogic Meson AO-CEC bindings

The Amlogic SoCs embeds a standalone CEC Controller, this patch adds this
device bindings.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>