media: dt-bindings: aspeed,video-engine: Convert to json schema

Convert aspeed-video.txt to yaml format.
Update aspeed-video.txt to aspeed,video-engine.yaml in MAINTAINER file.

Signed-off-by: Jammy Huang <jammy_huang@aspeedtech.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Andrew Jeffery <andrew@codeconstruct.com.au>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>