Convert analogix_dp-rockchip.txt to yaml.

Changed:
  Add power-domains property
  File name
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/88a5a9e3-9bc8-5966-22ec-5bdb1fa7a5b1@gmail.com