[llvm] [AArch64][SVE] Add lowering for PARTIAL_REDUCE_U/SMLA to USDOT (PR #131327)

[Nicholas Guy via llvm-commits]

NickGuy-Arm wrote:

Converting this to a draft, as an acceptable solution will likely require more effort than I can afford right now. I'll revisit it in the future.

https://github.com/llvm/llvm-project/pull/131327