Also add the late notes for Mips in the current release note

llvm-svn: 129122

llvm/docs/ReleaseNotes.html

@@ -749,6 +749,10 @@ it run faster:</p>
   directly writing out mach-o object files.  No one seems interested in finishing
   this final step though.</li>
 
+<li>Mips: Improved o32 ABI support, including better varags handling.
+More instructions supported in codegen: madd, msub, rotr, rotrv and clo.
+It also now supports lowering block addresses.</li>
+
 </ul>
 </div>