ksm: fix typo in comment

Spelling mistake (triple letters) in comment.  Detected with the help of
Coccinelle.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Julia Lawall <[email protected]>
Reviewed-by: Muchun Song <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

mm/ksm.c

@@ -1590,7 +1590,7 @@ static struct page *stable_tree_search(struct page *page)
 		 * the rbtree instead as a regular stable_node (in
 		 * order to collapse the stable_node chain if a single
 		 * stable_node dup was found in it). In such case the
-		 * stable_node is overwritten by the calleee to point
+		 * stable_node is overwritten by the callee to point
 		 * to the stable_node_dup that was collapsed in the
 		 * stable rbtree and stable_node will be equal to
 		 * stable_node_dup like if the chain never existed.