drm/amd/display: Clear edid when unplug mst connector

[Why]
When unplug one sst monitor from a mst hub and plug in the same
port with another sst monitor, we don't read the corresponding
edid. That's because we detect there is already an edid stored in
aconnector->edid which is a stale one.

[How]
Clean up aconnector->edid when unplug mst connector.
Reviewed-by: NHersen Wu <hersen.wu@amd.com>
Acked-by: NSolomon Chiu <solomon.chiu@amd.com>
Signed-off-by: NWayne Lin <Wayne.Lin@amd.com>
Tested-by: NDaniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c

@@ -160,6 +160,7 @@ amdgpu_dm_mst_connector_early_unregister(struct drm_connector *connector)
 
 		dc_sink_release(dc_sink);
 		aconnector->dc_sink = NULL;
+		aconnector->edid = NULL;
 	}
 	drm_modeset_unlock(&root->mst_mgr.base.lock);
 }
@@ -411,6 +412,7 @@ dm_dp_mst_detect(struct drm_connector *connector,
 
 		dc_sink_release(aconnector->dc_sink);
 		aconnector->dc_sink = NULL;
+		aconnector->edid = NULL;
 	}
 
 	return connection_status;