Update release notes for 6.0

Added support for PCI and KASAN on 64-bit UML and updated the version
number to 6.0

Change-Id: Ie3f5fbac2918bedc72640bfc63fface20395b69a
Signed-off-by: Sadiya Kazi <sadiyakazi@google.com>
diff --git a/release_notes.rst b/release_notes.rst
index f565423..7bc187a 100644
--- a/release_notes.rst
+++ b/release_notes.rst
@@ -254,10 +254,10 @@
 
   - E.g. instead of ``['-m 256']``, do ``['-m', '256']``
 
-.. _v5.20:
+.. _v6.0:
 
-5.20 (tentative)
-================
+6.0 (tentative)
+===============
 
 - Overhaul support for building tests as modules
 
@@ -277,4 +277,8 @@
 
 - Taint the kernel if any KUnit tests run.
 
-  - Added a new ``TAINT_TEST`` flag, shows up as ``'N'``.
+  - Add a new ``TAINT_TEST`` flag, shows up as ``'N'``.
+
+- Add support for KASAN to run on 64-bit UML.
+
+- By default, enable PCI support under UML.