[clang] [HLSL][NFC] Move packoffset validation to separate function and calculate offsets in bytes (PR #121989)

[Helena Kotas via cfe-commits]

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@@ -219,33 +223,41 @@ void SemaHLSL::ActOnFinishBuffer(Decl *Dcl, SourceLocation RBrace) {
     }
   }
 
-  if (HasPackOffset && HasNonPackOffset)
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hekota wrote:

This is best to review with 'Hide whitespaces'

https://github.com/llvm/llvm-project/pull/121989