[llvm] [LV][SVE] Recognize potential DOT sequences and use a wider VF (PR #69587)

[Paul Walker via llvm-commits]

https://github.com/paulwalker-arm requested changes to this pull request.

Let me know if requesting changes is a little harsh but given I'd like us to try a different path (https://discourse.llvm.org/t/rfc-is-a-more-expressive-way-to-represent-reductions-useful) I'm assuming this will significant affect this PR.

https://github.com/llvm/llvm-project/pull/69587