arm64: dts: rockchip: fix rk3399 dsi node

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

Signed-off-by: Johan Jonker <jbx6244@gmail.com>
Link: https://lore.kernel.org/r/1e019e9e-a8da-3d57-2770-f6b81bbbf591@gmail.com


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