[llvm] [DirectX] Do not flatten GEP chains for unsupported types (PR #150484)

[Joshua Batista via llvm-commits]

https://github.com/bob80905 approved this pull request.

Looks to me like line 298 is the way out for parent GEPs that have a struct type or otherwise unsupported type. 
Might be worth updating the comment with something like, "we also don't need to do any flattening for children GEPs if the type is unsupported, e.g., a struct"
But that's a nit / verifying my understanding is correct. Code / test LGTM

https://github.com/llvm/llvm-project/pull/150484