[clang] [mlir][llvm] Fix elem type passing into `getelementptr` (PR #68136)

[Oleksandr Alex Zinenko via cfe-commits]

ftynse wrote:

What I meant in the comment was that MLIR doesn't need to make a hard switch to using opaque pointers and immediately turn off typed pointers. I didn't really imply that an operations in the IR should freely mix the two. Typed pointers should and will be removed from the LLVM dialect as well. I consider any significant investment into typed pointer support, let alone a "mixed mode", a waste of time. Since this PR fixes a crash, I'm fine with it landing as is instead of spending cycles on an arguably better fix that will get removed within months as I hope opaque pointers to be gone from the dialect by the next release. Improving verifiers otherwise is greatly appreciated!

https://github.com/llvm/llvm-project/pull/68136