drm/msm/dp: config aux switch only on configure/disconnect

Avoid aux switch config during stream on/off as it moves mst
branch device into wrong state. Perform the aux switch config
only on receiving real configure/disconnect events.

CRs-Fixed: 2327801
Change-Id: I2a22a830387f5da71f9a2341274de7b1b0e1e99a
Signed-off-by: Govinda Rajulu Chenna <gchenna@codeaurora.org>