lockd: introduce new function to encode private argument in SM_MON requests

Clean up: refactor the encoding of the opaque 16-byte private argument in
xdr_encode_mon().  This will be updated later to support IPv6 addresses.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/include/linux/lockd/sm_inter.h b/include/linux/lockd/sm_inter.h
index 22a6458..5a5448b 100644
--- a/include/linux/lockd/sm_inter.h
+++ b/include/linux/lockd/sm_inter.h
@@ -19,6 +19,7 @@
 #define SM_NOTIFY	6
 
 #define SM_MAXSTRLEN	1024
+#define SM_PRIV_SIZE	16
 
 /*
  * Arguments for all calls to statd