dt-bindings: display: convert rockchip rk3066 hdmi bindings to yaml

Current dts files with 'hdmi' nodes for rk3066 are manually verified.
In order to automate this process rockchip,rk3066-hdmi.txt
has to be converted to yaml.

Signed-off-by: Johan Jonker <jbx6244@gmail.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20200403133630.7377-1-jbx6244@gmail.com