[llvm] [SPIR-V] Remove metadata-driven kernel arg Volatile decoration (PR #215790)

[Dmitry Sidorov via llvm-commits]

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

LGTM

Would be nice to hear from @michalpaszkowski if this function is actually a load-bearing.

https://github.com/llvm/llvm-project/pull/215790