Misc doc edits

howto/code/release-bugfix.rst
-----------------------------
  o Clarify a few items

release_notes/voltha_2.12.rst
-----------------------------
  o Update version and URLs for component bng.
  o Update version and URLs for component olttopology.
  o Remove pppoeagent from the VOLTHA release matrix, present in ONOS.

Change-Id: Ib035bada96466bb526674bf5bb0869a0b11a0bc5
diff --git a/howto/code/linting.rst b/howto/code/linting.rst
index 78f0ce1..e500f4c 100644
--- a/howto/code/linting.rst
+++ b/howto/code/linting.rst
@@ -1,3 +1,5 @@
+.. _code--makefile-lint-targets
+
 ======================================
 Makefile Lint Targets: Syntax Checking
 ======================================