Spec: include port mod failed errors

doc/of-spec/appendix.tex

@@ -395,6 +395,11 @@ For the \verb|OFPET_FLOW_MOD_FAILED| error \verb|type|, the following \verb|code
 \input{enum/ofp_flow_mod_failed_code}
 The \verb|data| field contains at least 64 bytes of the failed request.
 \\\\
+For the \verb|OFPET_PORT_MOD_FAILED| error \verb|type|, the following \verb|code|s are currently defined:
+
+\input{enum/ofp_port_mod_failed_code}
+The \verb|data| field contains at least 64 bytes of the failed request.
+\\\\
 For the \verb|OFPET_QUEUE_OP_FAILED| error \verb|type|, the following \verb|code|s are currently defined:
 
 \input{enum/ofp_queue_op_failed_code}