[llvm] [SPIR-V] Ensure that we don't have a dangling BlockAddress constants after internal intrinsic 'spv_switch' is processed (PR #92390)

[Nathan Gauër via llvm-commits]

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

Thanks for fixing! 😊

https://github.com/llvm/llvm-project/pull/92390