drm/msm/dp: handle AUX transactions during quick connect/disconnect

Handle AUX transactions graciously during when the DP cable is
disconnected while the DP On sequence is under process. This use-case
can happen when the connect/disconnect events are very quick or the
DP cable is a faulty one where the DP On sequence takes a long time
to finish due to continuous AUX timeout errors and DP cable is
disconnected during the process.

Change-Id: I4099ac714790be9357ff09fa4640859d35704ff4
Signed-off-by: Padmanabhan Komanduru <pkomandu@codeaurora.org>