[llvm] [llvm-readobj] enable demangle option for the xcoff object file (PR #78455)

[James Henderson via llvm-commits]

================
@@ -104,6 +99,11 @@ file formats.
 
  Display the needed libraries.
 
+.. option:: --no-demangle
+
+ Not demangle symbol names in the output; the option only is for ELF and
----------------
jh7370 wrote:

```suggestion
 Not demangle symbol names in the output; the option is only for ELF and
```

https://github.com/llvm/llvm-project/pull/78455