list.h: new helper - hlist_add_fake()

Make node look as if it was on hlist, with hlist_del()
working correctly.  Usable without any locking...

Convert a couple of places where we want to do that to
inode->i_hash.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/hfsplus/inode.c b/fs/hfsplus/inode.c
index 7844928..8afd7e8 100644
--- a/fs/hfsplus/inode.c
+++ b/fs/hfsplus/inode.c
@@ -211,7 +211,7 @@
 	 * appear hashed, but do not put on any lists.  hlist_del()
 	 * will work fine and require no locking.
 	 */
-	inode->i_hash.pprev = &inode->i_hash.next;
+	hlist_add_fake(&inode->i_hash);
 
 	mark_inode_dirty(inode);
 out: