[clang] [clang][CodeGen][SPIR-V] Fix incorrect SYCL usage, implement missing interface (PR #109415)

[Arvind Sudarsanam via cfe-commits]

https://github.com/asudarsa approved this pull request.

LGTM. Addition of new tests can be done in this PR or a follow-up PR.
Thanks

https://github.com/llvm/llvm-project/pull/109415