docs/vm: rename documentation files to .rst

Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
diff --git a/mm/frontswap.c b/mm/frontswap.c
index fec8b50..4f5476a 100644
--- a/mm/frontswap.c
+++ b/mm/frontswap.c
@@ -3,7 +3,7 @@
  *
  * This code provides the generic "frontend" layer to call a matching
  * "backend" driver implementation of frontswap.  See
- * Documentation/vm/frontswap.txt for more information.
+ * Documentation/vm/frontswap.rst for more information.
  *
  * Copyright (C) 2009-2012 Oracle Corp.  All rights reserved.
  * Author: Dan Magenheimer