Silence warning

Signed-off-by: Ralph Castain <rhc@open-mpi.org>

orte/mca/rmaps/base/rmaps_base_ranking.c

@@ -378,7 +378,7 @@ static int rank_by(orte_job_t *jdata,
              * algorithm, but this works for now.
              */
             i = 0;
-            while (cnt < app->num_procs && i < node->num_procs) {
+            while (cnt < app->num_procs && i < (int)node->num_procs) {
                 /* get the next object */
                 obj = (hwloc_obj_t)opal_pointer_array_get_item(&objs, i % num_objs);
                 if (NULL == obj) {