sway/main.c: simplify free'ing by switching to the helper method

sway/main.c

@@ -224,9 +224,7 @@ int main(int argc, char **argv) {
 		wlc_run();
 	}
 
-	if (input_devices) {
+	list_free(input_devices);
-		free(input_devices);
-	}
 
 	ipc_terminate();