libmemif: add private header size field

Change-Id: I09567c8ee9c92e91918840f80942a005069d9842
Signed-off-by: Jakub Grajciar <jgrajcia@cisco.com>
diff --git a/extras/libmemif/src/libmemif.h b/extras/libmemif/src/libmemif.h
index 14c4503..e1f96f9 100644
--- a/extras/libmemif/src/libmemif.h
+++ b/extras/libmemif/src/libmemif.h
@@ -74,6 +74,7 @@
   MEMIF_ERR_UNKNOWN_MSG,	/*!< unknown message type */
   MEMIF_ERR_POLL_CANCEL,	/*!< memif_poll_event() was cancelled */
   MEMIF_ERR_MAX_RING,		/*!< too large ring size */
+  MEMIF_ERR_PRIVHDR,		/*!< private hdrs not supported */
 } memif_err_t;
 
 /**