[llvm] [AArch64] Turn MaxInterleaveFactor into a subtarget feature (PR #171088)

[Florian Hahn via llvm-commits]

https://github.com/fhahn approved this pull request.

LGTM, thanks.

This presumably also allows specifying the target feature to use max interleave factor 4 for CPUs that do not have it (or disable it via the target-feature if for CPUs that do). MIght be good to add a test that just uses the target feature?

https://github.com/llvm/llvm-project/pull/171088