[llvm] [SPIR-V] Emit OpConstant instead of OpConstantNull to conform to NonSemantic.Shader.DebugInfo.100 DebugTypeBasic's flags definition (PR #118333)

[Vyacheslav Levytskyy via llvm-commits]

VyacheslavLevytskyy wrote:

> @VyacheslavLevytskyy: It looks like this PR failed to remove [the XFAIL added to the test](https://github.com/llvm/llvm-project/commit/c7e14689dd8bdf4b18dccb18895a9b80c225dc53) when fixing the issue. We are hitting an unexpected pass causing testing to fail in our pipeline now due to this.

Thank you, this should be fixed in the main branch already.

https://github.com/llvm/llvm-project/pull/118333