Documentation: move locks.txt in filesystems/

This documentation (about file locking) belongs in filesystems/.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
diff --git a/Documentation/filesystems/00-INDEX b/Documentation/filesystems/00-INDEX
index e801076..599593a 100644
--- a/Documentation/filesystems/00-INDEX
+++ b/Documentation/filesystems/00-INDEX
@@ -52,6 +52,8 @@
 	- info and mount options for the ISO 9660 (CDROM) filesystem.
 jfs.txt
 	- info and mount options for the JFS filesystem.
+locks.txt
+	- info on file locking implementations, flock() vs. fcntl(), etc.
 mandatory-locking.txt
 	- info on the Linux implementation of Sys V mandatory file locking.
 ncpfs.txt