hwloc: fix misc memory leak

as reported by Coverity with CID 1270441
(previous commit open-mpi/ompi@c25185f3a9 did not fully fix that one)

opal/mca/hwloc/base/hwloc_base_util.c

@@ -2078,6 +2078,7 @@ int opal_hwloc_get_sorted_numa_list(hwloc_topology_t topo, char* device_name, op
                     if (!strcmp(device_name, "auto")) {
                         count = find_devices(topo, &device_name);
                         if (count > 1) {
+                            free(device_name);
                             return count;
                         }
                     }