drm/rockchip: analogix_dp: add rk3399 eDP support

RK3399 and RK3288 shared the same eDP IP controller, only some light
difference with VOP configure and GRF configure.

Signed-off-by: Yakir Yang <ykk@rock-chips.com>
Acked-by: Mark Yao <mark.yao@rock-chips.com>
Reviewed-by: Tomasz Figa <tomasz.figa@chromium.com>
Reviewed-by: Sean Paul <seanpaul@chromium.org>