Improve fabric.p4 with BNG support

Change-Id: I08f8991d8cf432785e0c409354b6301c8983bfb4
diff --git a/pipelines/fabric/src/main/resources/include/parser.p4 b/pipelines/fabric/src/main/resources/include/parser.p4
index e0f9fc5..e234676 100644
--- a/pipelines/fabric/src/main/resources/include/parser.p4
+++ b/pipelines/fabric/src/main/resources/include/parser.p4
@@ -90,6 +90,7 @@
     state parse_pppoe {
         packet.extract(hdr.pppoe);
         transition select(hdr.pppoe.protocol) {
+            PPPOE_PROTOCOL_MPLS: parse_mpls;
             PPPOE_PROTOCOL_IP4: parse_ipv4;
 #ifdef WITH_IPV6
             PPPOE_PROTOCOL_IP6: parse_ipv6;