[Why]
Observe that we have several problems while releasing remote dc_sink
under mst cases.

- When unplug mst branch device from the source, we now try to free all
  remote dc_sinks in dm_helpers_dp_mst_stop_top_mgr(). However, there are
  bugs while we're releasing dc_sinks here. First of all,
  link->remote_sinks[] array get shuffled within
  dc_link_remove_remote_sink(). As the result, increasing the array index
  within the releasing loop is wrong. Secondly, it tries to call
  dc_sink_release() to release the dc_sink of the same aconnector every
  time in the loop. Which can't release dc_sink of all aconnector in the
  mst topology.
- There is no code path for us to release remote dc_sink for disconnected
  sst monitor which unplug event is notified by CSN sideband message. Which
  means we'll use stale dc_sink data to represent later on connected
  monitor. Also, has chance to break the maximum remote dc_sink number
  constraint.

[How]
Distinguish unplug event of mst scenario into 2 cases.

* Unplug sst/legacy stream sink off the mst topology
- Release related remote dc_sink in detec_ctx().

* Unplug mst branch device off the mst topology
- Release related remote dc_sink in early_unregister()
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Reviewed-by: Aurabindo Jayamohanan Pillai <Aurabindo.Pillai@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Acked-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Wayne Lin <Wayne.Lin@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>