[llvm] [VPlan] Simplify Plan's entry in removeBranchOnConst. (PR #154510)

[Florian Hahn via llvm-commits]

================
@@ -970,7 +970,7 @@ loop:
   %red.next = fadd double %for, %red
   %for.next = sitofp i32 %iv to double
   %iv.next = add nsw i32 %iv, 1
-  %ec = icmp eq i32 %iv.next, 1025
+  %ec = icmp eq i32 %iv.next, %n
----------------
fhahn wrote:

Without it there would be no merge phis in `scalar.ph`, which seems to be what the test needs to check.

https://github.com/llvm/llvm-project/pull/154510