Mcast rewrite optimisations

hard code the address mask offsets. This are protocol specific and only used on ethernet when used at all.

Change-Id: Ib1f6f33682f53254ffbb5a241a1583e65420e0c7
Signed-off-by: Neale Ranns <nranns@cisco.com>
diff --git a/src/vnet/interface.c b/src/vnet/interface.c
index b07a9ba..13ad65e 100644
--- a/src/vnet/interface.c
+++ b/src/vnet/interface.c
@@ -1534,7 +1534,7 @@
 	 vnet_build_rewrite_for_sw_interface (vnm,
 					      sw_if_index,
 					      adj_get_link_type (ai),
-					      NULL), 0, 0);
+					      NULL), 0);
       break;
     case IP_LOOKUP_NEXT_DROP:
     case IP_LOOKUP_NEXT_PUNT: