ReleaseNotes: mention removal of Intel MPX

MaskRay · MaskRay · commit 4384a21fdcaa · 2022-02-14T12:00:05.000-08:00
diff --git a/llvm/docs/ReleaseNotes.rst b/llvm/docs/ReleaseNotes.rst
@@ -113,6 +113,8 @@ Changes to the X86 Target
 During this release ...
 
 * Support for ``AVX512-FP16`` instructions has been added.
+* Removed incomplete support for Intel MPX.
+  (`D111517 <https://reviews.llvm.org/D111517>`_)
 
 Changes to the AMDGPU Target
 -----------------------------
