Documentation: update LXR web link

Update LXR (Linux cross reference) web link.
Signed-off-by: Harry Wei <harryxiyou@gmail.com>
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Documentation/HOWTO

@@ -209,7 +209,7 @@ tools.  One such tool that is particularly recommended is the Linux
 Cross-Reference project, which is able to present source code in a
 self-referential, indexed webpage format. An excellent up-to-date
 repository of the kernel code may be found at:
-	http://users.sosdg.org/~qiyong/lxr/
+	http://lxr.linux.no/+trees
 
 
 The development process