drm: rockchip: Provide ddc symlink in inno_hdmi sysfs directory

Use the ddc pointer provided by the generic connector.

Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Acked-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/ <a1f778d328328f15300338600bb2400850717300.1566845537.git.andrzej.p@collabora.com