5045 use atomic_{inc,dec}_* instead of atomic_add_*

@@ -1556,11 +1556,11 @@
         ill_t           *ill;
         ip_recv_attr_t  iras;
         boolean_t       dummy;
 
         /* We assign an IP ident for nice errors */
-        ipha->ipha_ident = atomic_add_32_nv(identp, 1);
+        ipha->ipha_ident = atomic_inc_32_nv(identp);
 
         BUMP_MIB(&ipst->ips_ip_mib, ipIfStatsOutNoRoutes);
 
         if (ire->ire_type & IRE_NOROUTE) {
                 /* A lack of a route as opposed to RTF_REJECT|BLACKHOLE */