arm64: dts: rockchip: fix rk3399 dp node

Use generic node name for rk3399.dtsi dp node.
With the conversion of rockchip,analogix-dp.yaml a port@1 node
is required, so add a node with label edp_out.
Also restyle.

Signed-off-by: Johan Jonker <jbx6244@gmail.com>
Link: https://lore.kernel.org/r/f6008819-db9b-0944-3f5b-5522b7cd8a8d@gmail.com


Signed-off-by: Heiko Stuebner <heiko@sntech.de>