[clang] [Clang][docs] Modify generator for HLSL semantics documentation (PR #157841)

[Erich Keane via cfe-commits]

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@@ -5209,6 +5209,14 @@ class SpellingList {
                              Other.Spellings[Kind].end());
     }
   }
+
+  unsigned getSpellingCount() const {
+    unsigned Count = 0;
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erichkeane wrote:

`return llvm::accumulate(Spellings, 0, [](const auto &I) {return I.size() ? 1 : 0; });`

https://github.com/llvm/llvm-project/pull/157841