[clang] [clang:frontend] Move helper functions to common location for SemaSPIRV (PR #125045)

[Mats Jun Larsen via cfe-commits]

https://github.com/junlarsen commented:

Each file should have license headers, ref https://llvm.org/docs/CodingStandards.html#file-headers

https://github.com/llvm/llvm-project/pull/125045