nfs_clone_sb_security(): simplify the check for server bogosity

We used to check ->i_op for being nfs_dir_inode_operations.  With
separate inode_operations for v3 and v4 that became bogus, but
rather than going for protocol-dependent comparison we could've
just checked ->i_fop instead; _that_ is the same for all protocol
versions.
Reviewed-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

fs/nfs/super.c

@@ -2578,7 +2578,7 @@ int nfs_clone_sb_security(struct super_block *s, struct dentry *mntroot,
 	unsigned long kflags = 0, kflags_out = 0;
 
 	/* clone any lsm security options from the parent to the new sb */
-	if (d_inode(mntroot)->i_op != NFS_SB(s)->nfs_client->rpc_ops->dir_inode_ops)
+	if (d_inode(mntroot)->i_fop != &nfs_dir_operations)
 		return -ESTALE;
 
 	if (NFS_SB(s)->caps & NFS_CAP_SECURITY_LABEL)