dt-bindings: display: rockchip: update DSI controller

This patch update describe panel/port links, including
unit addresses in documentation of device tree bindings
for the rockchip DSI controller based on the Synopsys
DesignWare MIPI DSI host controller.

Signed-off-by: Nickey Yang <nickey.yang@rock-chips.com>
Reviewed-by: Brian Norris <briannorris@chromium.org>
Reviewed-by: Rob Herring <robh@kernel.org>
[this seems to have gotten lost when the original dsi-series was applied]
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20181001123845.11818-5-heiko@sntech.de