[llvm] [AArch64] Update IssueWidth for Neoverse V1, N1, N3 (PR #154495)

[David Green via llvm-commits]

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

I would go with a IssueWidth of 4 for NeoverseN1, as I believe that matches reality better, but either way this LGTM.

https://github.com/llvm/llvm-project/pull/154495