bgpd: fix regression in ORF procesing (BZ#688)

This issue has been pointed out by Lou Berger and Tim Browski.

* bgp_packet.c
  * bgp_route_refresh_receive(): restore if() condition, which was
    broken by commit fdbc8e77c88f751924299d0bc752371d5cc31116
diff --git a/bgpd/bgp_packet.c b/bgpd/bgp_packet.c
index 4854f1d..2c0113d 100644
--- a/bgpd/bgp_packet.c
+++ b/bgpd/bgp_packet.c
@@ -2054,7 +2054,7 @@
 		      break;
 		    }
 		  ok = ((p_end - p_pnt) >= sizeof(u_int32_t)) ;
-		  if (!ok)
+		  if (ok)
 		    {
 		      memcpy (&seq, p_pnt, sizeof (u_int32_t));
                       p_pnt += sizeof (u_int32_t);