drm/msm/dp: signal the hotplug disconnect in the event handler

Signal the hotplug disconnect event to the audio side in the
event handler so that they are notified earlier and have more
time to process the disconnect event.

Changes in v2: none
Changes in v3: none
Changes in v4: rebase on top of latest patchset of dependency
Changes in v5: rebase on top of latest patchset of dependency
Changes in v6: none

Signed-off-by: Abhinav Kumar <abhinavk@codeaurora.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>