drm/msm/dp: use dp_msm_sim for dp-mst simulation

Revert changes in dp mst topology manager and use dp_msm_sim bridge
at aux layer to implement dp-mst simulation.

Change-Id: I863649f901ac918f65c9078e6a2f1b6931d19e3a
Signed-off-by: Xiaowen Wu <wxiaowen@codeaurora.org>