[docs] Add the release notes about Debug Entry Values

Note that x86, arm and aarch64 targets support the Debug Entry Values
feature by default.

Differential Revision: https://reviews.llvm.org/D77494

Author: Djordje Todorovic

llvm/docs/ReleaseNotes.rst

@@ -134,6 +134,18 @@ Changes to the Go bindings
 Changes to the DAG infrastructure
 ---------------------------------
 
+
+Changes to the Debug Info
+---------------------------------
+
+* LLVM now supports the debug entry values (DW_OP_entry_value) production for
+  the x86, ARM, and AArch64 targets by default. Other targets can use
+  the utility by using the experimental option ("-debug-entry-values").
+  This is a debug info feature that allows debuggers to recover the value of
+  optimized-out parameters by going up a stack frame and interpreting the values
+  passed to the callee. The feature improves the debugging user experience when
+  debugging optimized code.
+
 Changes to LLDB
 ===============