[llvm] [SPIR-V] Fix generation of invalid SPIR-V in cases of of bitcasts between pointers and multiple null pointers used in the input LLVM IR (PR #118298)

[Vyacheslav Levytskyy via llvm-commits]

https://github.com/VyacheslavLevytskyy edited https://github.com/llvm/llvm-project/pull/118298