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

[Cullen Rhodes via llvm-commits]

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@@ -15,7 +15,7 @@
 //===----------------------------------------------------------------------===//
 
 def NeoverseN1Model : SchedMachineModel {
-  let IssueWidth            =   8; // Maximum micro-ops dispatch rate.
+  let IssueWidth            =   3; // Maximum micro-ops dispatch rate.
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c-rhodes wrote:

can we update these comments to match the v2 scheduler following this discussion: https://github.com/llvm/llvm-project/pull/142565#discussion_r2126798020

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