[llvm] [AArch64][GlobalISel] Select integer vector reductions into GPRs (PR #212976)

[Cullen Rhodes via llvm-commits]

c-rhodes wrote:

> end to end ir tests are better

regbankselect will select FPR for result so unless I'm missing something I don't think it's possible to test this differently

https://github.com/llvm/llvm-project/pull/212976