dt-bindings: display: Add Document for Rockchip Soc LVDS

This patch add Document for Rockchip Soc RK3288 LVDS,
This based on the patches from Mark yao and Heiko Stuebner.

Signed-off-by: Mark yao <mark.yao@rock-chips.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Sandy Huang <hjc@rock-chips.com>
Reviewed-by: Mark Yao <mark.yao@rock-chips.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/1504351729-135932-1-git-send-email-hjc@rock-chips.com