[llvm] [AArch64][SVE] Support lowering masked loads/stores of <4 x bf16> and <8 x bf16> (PR #208744)

[Sander de Smalen via llvm-commits]

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sdesmalen-arm wrote:

There's no harm in adding the extra test. We can always improve codegen for it in a future commit, the intent was more to ensure that the case compiles (correctly).

https://github.com/llvm/llvm-project/pull/208744