[llvm] Add support for DFP IR type. (PR #69718)

[Tom Honermann via llvm-commits]

tahonermann wrote:

Hi, Zahira. We haven't been pushing DFP changes to upstream yet. Could you submit a PR to [the dfp branch of my fork](https://github.com/tahonermann/llvm-project/tree/dfp) instead?

https://github.com/llvm/llvm-project/pull/69718