[llvm] [HLSL] Leave out entryname from string table for PSV versions < 3 (PR #191528)

[via llvm-commits]

================
@@ -770,8 +770,11 @@ void DXContainerYAML::PSVInfo::mapInfoForVersion(yaml::IO &IO) {
   IO.mapRequired("NumThreadsY", Info.NumThreadsY);
   IO.mapRequired("NumThreadsZ", Info.NumThreadsZ);
 
-  if (Version == 2)
+  if (Version == 2) {
+    if (!IO.outputting())
+      IO.mapOptional("EntryName", EntryName);
----------------
joaosaffran wrote:

@bob80905 

Sorry, the optional mapping should happen after the v1 check and before the v2, that way we know you are handling v2 checks. However, ideally we shouldn't check for versions in the yaml, but that is not a refactor i expect to be done in that change.

The change bellow should align with the other changes I mention in here, though https://github.com/llvm/llvm-project/pull/191528#discussion_r3096995333

```cpp
      IO.mapOptional("EntryName", EntryName);
     if (Version == 2)
         return;
```

https://github.com/llvm/llvm-project/pull/191528