[llvm] [LV][NFC] Remove remaining uses of undef in tests (PR #169357)

[David Sherwood via llvm-commits]

================
@@ -44,19 +44,19 @@ for.body.i.i.i:
 for.inc.i.i.i:
   %indvars.iv.next = add i64 %indvars.iv, 1
   %lftr.wideiv = trunc i64 %indvars.iv.next to i32
-  %exitcond = icmp ne i32 %lftr.wideiv, undef
+  %exitcond = icmp ne i32 %lftr.wideiv, poison
----------------
david-arm wrote:

Actually, we can use a live-in here.

https://github.com/llvm/llvm-project/pull/169357