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

[Nicholas Guy via llvm-commits]

NickGuy-Arm wrote:

This PR implicitly depends on https://github.com/llvm/llvm-project/pull/130935 and https://github.com/llvm/llvm-project/pull/131326

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