laptops: move laptop-mode.txt to Documentation/laptops/

Move laptop-mode.txt into the laptops/ sub-directory to consolidate
laptop doc files there.

Update references to the file's location.

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Len Brown <len.brown@intel.com>
diff --git a/Documentation/laptops/00-INDEX b/Documentation/laptops/00-INDEX
index 729c2c0..ee5692b 100644
--- a/Documentation/laptops/00-INDEX
+++ b/Documentation/laptops/00-INDEX
@@ -2,6 +2,8 @@
 	- This file
 acer-wmi.txt
 	- information on the Acer Laptop WMI Extras driver.
+laptop-mode.txt
+	- how to conserve battery power using laptop-mode.
 sony-laptop.txt
 	- Sony Notebook Control Driver (SNC) Readme.
 sonypi.txt