netinet6: Fix two typos in source code comments

- s/adddress/address/

MFC after:	3 days

sys/netinet6/nd6_nbr.c

@@ -262,7 +262,7 @@ nd6_ns_input(struct mbuf *m, int off, int icmp6len)
 	}
 	if (ifa == NULL) {
 		/*
-		 * We've got an NS packet, and we don't have that adddress
+		 * We've got an NS packet, and we don't have that address
 		 * assigned for us.  We MUST silently ignore it.
 		 * See RFC2461 7.2.3.
 		 */

sys/netinet6/scope6.c

@@ -525,7 +525,7 @@ in6_getscopezone(const struct ifnet *ifp, int scope)
 }
 
 /*
- * Extracts scope from adddress @dst, stores cleared address
+ * Extracts scope from address @dst, stores cleared address
  * inside @dst and zone inside @scopeid
  */
 void