drm/display/dp_mst: Don't validate port refs in drm_dp_check_and_send_link_address()

Drive-by cleanup, we don't need to validate the port references here as we
already previously went through the effort of refactoring things such that
we're guaranteed to be able to access ->mstb and ->port safely from
drm_dp_check_and_send_link_address(), since the only two places in the
codebase that drop an MST reference in such a way that it would remove it
from the topology are both protected under probe_lock.

Thanks for that, past Lyude!
Signed-off-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Wayne Lin <Wayne.Lin@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220602201757.30431-2-lyude@redhat.com

drivers/gpu/drm/display/drm_dp_mst_topology.c

@@ -2667,25 +2667,15 @@ static int drm_dp_check_and_send_link_address(struct drm_dp_mst_topology_mgr *mg
 	}
 
 	list_for_each_entry(port, &mstb->ports, next) {
-		struct drm_dp_mst_branch *mstb_child = NULL;
-
-		if (port->input || !port->ddps)
+		if (port->input || !port->ddps || !port->mstb)
 			continue;
 
-		if (port->mstb)
-			mstb_child = drm_dp_mst_topology_get_mstb_validated(
-			    mgr, port->mstb);
-
-		if (mstb_child) {
-			ret = drm_dp_check_and_send_link_address(mgr,
-								 mstb_child);
-			drm_dp_mst_topology_put_mstb(mstb_child);
+		ret = drm_dp_check_and_send_link_address(mgr, port->mstb);
 		if (ret == 1)
 			changed = true;
 		else if (ret < 0)
 			return ret;
 	}
-	}
 
 	return changed;
 }