drm/msm/dp: fixes wrong connection state caused by failure of link train

drm/msm/dp: fixes wrong connection state caused by failure of link train

Connection state is not set correctly happen when either failure of link
train due to cable unplugged in the middle of aux channel reading or
cable plugged in while in suspended state. This patch fixes these problems.
This patch also replace ST_SUSPEND_PENDING with ST_DISPLAY_OFF.

Changes in V2:
-- Add more information to commit message.

Changes in V3:
-- change base

Changes in V4:
-- add Fixes tag

Signed-off-by: Kuogee Hsieh <khsieh@codeaurora.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>