drm/bridge: analogix_dp: Fix connector and encoder cleanup

Since we are initing connector in the core driver and encoder in the
plat driver, let's clean them up in the right places.

Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
Signed-off-by: Thierry Escande <thierry.escande@collabora.com>
Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20180110162348.22765-3-thierry.escande@collabora.com