babeld: address some other compilation warnings.
diff --git a/babeld/route.h b/babeld/route.h
index dbb205d..e38f157 100644
--- a/babeld/route.h
+++ b/babeld/route.h
@@ -52,7 +52,7 @@
     short installed;
 };
 
-static inline int
+static inline unsigned short
 route_metric(const struct babel_route *route)
 {
     return route->metric;