[llvm] [SPIRV] Avoid OpQuantizeToF16 in SPIR-V kernel test (PR #158086)

[via llvm-commits]

YixingZhang007 wrote:

> LGTM. Can we spin off the OpQuantizeToF16 test to a new test and mark as xfail/unsupported, so we don't reduce test coverage?

Thanks for the suggestion! I have added the test for OpQuantizeToF16  in quantizeto16.ll and marked it as XFAIL. 

https://github.com/llvm/llvm-project/pull/158086