[clang] [HLSL][NFC] Remove RegisterBindingFlags struct (PR #108924)

[Helena Kotas via cfe-commits]

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@@ -41,6 +41,47 @@
 
 using namespace clang;
 
+enum class RegisterType { SRV, UAV, CBuffer, Sampler, C, I, Invalid };
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hekota wrote:

This is moved from below.

https://github.com/llvm/llvm-project/pull/108924