[llvm] [AArch64]Fix invalid use of ld1/st1 in stack alloc (PR #105518)

[Sander de Smalen via llvm-commits]

https://github.com/sdesmalen-arm approved this pull request.

LGTM, with two minor nits. Thanks for making the changes!

I agree there's follow-up work to support the case where either the offset is not a multiple of 2 or the first register is odd, but at least the code seems correct now.

https://github.com/llvm/llvm-project/pull/105518