NFS: Add a slot table to struct nfs_client for NFSv4.0 transport blocking

Anchor an nfs4_slot_table in the nfs_client for use with NFSv4.0
transport blocking.  It is initialized only for NFSv4.0 nfs_client's.

Introduce appropriate minor version ops to handle nfs_client
initialization and shutdown requirements that differ for each minor
version.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/include/linux/nfs_fs_sb.h b/include/linux/nfs_fs_sb.h
index d221243..fc83d3d 100644
--- a/include/linux/nfs_fs_sb.h
+++ b/include/linux/nfs_fs_sb.h
@@ -78,6 +78,9 @@
 	u32			cl_cb_ident;	/* v4.0 callback identifier */
 	const struct nfs4_minor_version_ops *cl_mvops;
 
+	/* NFSv4.0 transport blocking */
+	struct nfs4_slot_table	*cl_slot_tbl;
+
 	/* The sequence id to use for the next CREATE_SESSION */
 	u32			cl_seqid;
 	/* The flags used for obtaining the clientid during EXCHANGE_ID */