[clang] [llvm] [SemaHLSL] Correct descriptor range overflow validation (PR #159475)

[Tex Riddell via cfe-commits]

https://github.com/tex3d commented:

I think there may be a gap in this implementation allowing binding of overlapping size 1 range at UINT_MAX Offset; plus some other nits; see comments.

https://github.com/llvm/llvm-project/pull/159475