drm/rockchip: lvds: Remove include of drm_dp_helper.h

drm_dp_helper.h is not used by lvds driver

Signed-off-by: Andy Yan <andy.yan@rock-chips.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20240414120841.837661-1-andyshrk@163.com