fs: xattr_handler table should be const

The entries in xattr handler table should be immutable (ie const)
like other operation tables.

Later patches convert common filesystems. Uncoverted filesystems
will still work, but will generate a compiler warning.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/include/linux/fs.h b/include/linux/fs.h
index d51256b..6660db8 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1336,7 +1336,7 @@
 #ifdef CONFIG_SECURITY
 	void                    *s_security;
 #endif
-	struct xattr_handler	**s_xattr;
+	const struct xattr_handler **s_xattr;
 
 	struct list_head	s_inodes;	/* all inodes */
 	struct hlist_head	s_anon;		/* anonymous dentries for (nfs) exporting */