[llvm] [SPIRV] Fix APInt overflow in memset constant array creation (PR #180189)

[Nick Sarnie via llvm-commits]

sarnex wrote:

I don't think it's a real failure, I think it's a sporadic `libomp` failure reproted [here](https://github.com/llvm/llvm-project/issues/176451).

I don't see anything in the log about an IGC error, if there is one I think that's a different symptom than the reported one.

https://github.com/llvm/llvm-project/pull/180189