qstr: constify instances in nfs

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/include/linux/nfs_xdr.h b/include/linux/nfs_xdr.h
index c304a11..890b4ab 100644
--- a/include/linux/nfs_xdr.h
+++ b/include/linux/nfs_xdr.h
@@ -1543,7 +1543,7 @@
 			    struct nfs_fattr *, struct nfs4_label *);
 	int	(*setattr) (struct dentry *, struct nfs_fattr *,
 			    struct iattr *);
-	int	(*lookup)  (struct inode *, struct qstr *,
+	int	(*lookup)  (struct inode *, const struct qstr *,
 			    struct nfs_fh *, struct nfs_fattr *,
 			    struct nfs4_label *);
 	int	(*access)  (struct inode *, struct nfs_access_entry *);
@@ -1551,18 +1551,18 @@
 			    unsigned int);
 	int	(*create)  (struct inode *, struct dentry *,
 			    struct iattr *, int);
-	int	(*remove)  (struct inode *, struct qstr *);
+	int	(*remove)  (struct inode *, const struct qstr *);
 	void	(*unlink_setup)  (struct rpc_message *, struct inode *dir);
 	void	(*unlink_rpc_prepare) (struct rpc_task *, struct nfs_unlinkdata *);
 	int	(*unlink_done) (struct rpc_task *, struct inode *);
 	void	(*rename_setup)  (struct rpc_message *msg, struct inode *dir);
 	void	(*rename_rpc_prepare)(struct rpc_task *task, struct nfs_renamedata *);
 	int	(*rename_done) (struct rpc_task *task, struct inode *old_dir, struct inode *new_dir);
-	int	(*link)    (struct inode *, struct inode *, struct qstr *);
+	int	(*link)    (struct inode *, struct inode *, const struct qstr *);
 	int	(*symlink) (struct inode *, struct dentry *, struct page *,
 			    unsigned int, struct iattr *);
 	int	(*mkdir)   (struct inode *, struct dentry *, struct iattr *);
-	int	(*rmdir)   (struct inode *, struct qstr *);
+	int	(*rmdir)   (struct inode *, const struct qstr *);
 	int	(*readdir) (struct dentry *, struct rpc_cred *,
 			    u64, struct page **, unsigned int, int);
 	int	(*mknod)   (struct inode *, struct dentry *, struct iattr *,