thunderbolt: Only add device router DP IN to the head of the DP resource list

When pairing DP IN and DP OUT adapters for DisplayPort tunneling, we
should prioritize the possible external GPU DP IN adapters to take
advantage of the its capabilities. However the commit in question did
this for host router DP IN adapters too and that changes ordering of the
initial DP IN resources in such way that resuming from suspend may end
up using different resource and that may confuse the user.

Fix this so that we only put DP IN adapters of device routers to the top
of the resource list and leave host routers as is.

Fixes: 274baf69 ("thunderbolt: Add DP IN added last in the head of the list of DP resources")
Reported-by: Pengfei Xu <pengfei.xu@intel.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>

drivers/thunderbolt/tb.c

@@ -213,7 +213,17 @@ static void tb_add_dp_resources(struct tb_switch *sw)
 		if (!tb_switch_query_dp_resource(sw, port))
 			continue;
 
-		list_add(&port->list, &tcm->dp_resources);
+		/*
+		 * If DP IN on device router exist, position it at the
+		 * beginning of the DP resources list, so that it is used
+		 * before DP IN of the host router. This way external GPU(s)
+		 * will be prioritized when pairing DP IN to a DP OUT.
+		 */
+		if (tb_route(sw))
+			list_add(&port->list, &tcm->dp_resources);
+		else
+			list_add_tail(&port->list, &tcm->dp_resources);
+
 		tb_port_dbg(port, "DP IN resource available\n");
 	}
 }