kmemleak: fix reference to Documentation

Documentation/kmemleak.txt was moved to Documentation/dev-tools/kmemleak.rst,
this fixes the reference to the new location.

Link: http://lkml.kernel.org/r/1476544946-18804-1-git-send-email-andreas.platschek@opentech.atSigned-off-by: Andreas Platschek <andreas.platschek@opentech.at>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/kmemleak.c

@@ -19,7 +19,7 @@
  *
  *
  * For more information on the algorithm and kmemleak usage, please see
- * Documentation/kmemleak.txt.
+ * Documentation/dev-tools/kmemleak.rst.
  *
  * Notes on locking
  * ----------------