SubmittingPatches: update CodingStyle reference

Link to the internal up to date Coding Style document inside the Kernel
sources instead of an external one.
Signed-off-by: Luis de Bethencourt <luis@debethencourt.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/SubmittingPatches

@@ -796,7 +796,7 @@ NO!!!! No more huge patch bombs to linux-kernel@vger.kernel.org people!
   <https://lkml.org/lkml/2005/7/11/336>
 
 Kernel Documentation/CodingStyle:
-  <http://users.sosdg.org/~qiyong/lxr/source/Documentation/CodingStyle>
+  <Documentation/CodingStyle>
 
 Linus Torvalds's mail on the canonical patch format:
   <http://lkml.org/lkml/2005/4/7/183>