[VOL-5009] Update release notes

release_notes/voltha_2.12.rst
-----------------------------
  o Update version string and chart version for openolt-adapter.
  o Fixed a few extra fields in table formatting.

Change-Id: I060d26e3ca199a67aaee45ea8f38d87bfa650127
diff --git a/Makefile b/Makefile
index 1648ba7..ed57658 100644
--- a/Makefile
+++ b/Makefile
@@ -225,6 +225,14 @@
 	grep -i error _build/linkcheck/output.txt
 
 ## -----------------------------------------------------------------------
+## Intent: Summarize linkcheck failures
+## -----------------------------------------------------------------------
+.PHONY: lint-doc8-debug
+lint-doc8-debug : sterile
+	$(HIDE) @echo "Searching for cryptic failures"
+	-grep -i 'X <' release_notes/voltha_2.12.rst | grep -v '`__'
+
+## -----------------------------------------------------------------------
 ## Intent:
 ## -----------------------------------------------------------------------
 clean::