NFS: Update MNT and MNT3 reply decoding functions

Solder xdr_stream-based XDR decoding functions into the in-kernel mountd
client that are more careful about checking data types and watching for
buffer overflows.  The new MNT3 decoder includes support for auth-flavor
list decoding.

The "_sz" macro for MNT3 replies was missing the size of the file handle.
I've added this back, and included the size of the auth flavor array.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/nfsroot.c b/fs/nfs/nfsroot.c
index 24c1b93..8c55b27 100644
--- a/fs/nfs/nfsroot.c
+++ b/fs/nfs/nfsroot.c
@@ -490,6 +490,7 @@
 {
 	struct nfs_fh fh;
 	struct sockaddr_in sin;
+	unsigned int auth_flav_len = 0;
 	struct nfs_mount_request request = {
 		.sap		= (struct sockaddr *)&sin,
 		.salen		= sizeof(sin),
@@ -499,6 +500,7 @@
 		.protocol	= (nfs_data.flags & NFS_MOUNT_TCP) ?
 					XPRT_TRANSPORT_TCP : XPRT_TRANSPORT_UDP,
 		.fh		= &fh,
+		.auth_flav_len	= &auth_flav_len,
 	};
 	int status;