dt-bindings: media: amphion: add amphion video codec bindings

Add devicetree binding documentation for amphion
Video Processing Unit IP presents on NXP i.MX8Q

Signed-off-by: Ming Qian <ming.qian@nxp.com>
Signed-off-by: Shijie Qin <shijie.qin@nxp.com>
Signed-off-by: Zhou Peng <eagle.zhou@nxp.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>