drm/rockchip: Resume DP early

The DP needs to have resumed once the DRM driver calls
drm_atomic_helper_resume, otherwise the DP clock is still disabled when
the DRM core enables the DP bridge.

Would be nice to use device_pm_wait_for_dev to synchronize these
devices, but the DRM device doesn't know what specific implementation
this bridge has.

Signed-off-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Cc: Caesar Wang <wxt@rock-chips.com>
Cc: Douglas Anderson <dianders@chromium.org>
Cc: Heiko Stuebner <heiko@sntech.de>
Cc: Yakir Yang <ykk@rock-chips.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1465224813-7359-2-git-send-email-tomeu.vizoso@collabora.com