drm/msm/dp: configure AUX switch on connect/disconnect

Configure the AUX switch to enable AUX transactions on cable
connect, and to reset the switch once the cable is disconnected.

Change-Id: I716364616f3dcf6076b6901eab487a25608ef046
Signed-off-by: Tatenda Chipeperekwa <tatendac@codeaurora.org>