[llvm] [VPlan] Rename onlyFirstLaneUsed (NFC) (PR #166562)

[Luke Lau via llvm-commits]

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@@ -18,7 +18,7 @@ using namespace llvm::VPlanPatternMatch;
 
 bool vputils::onlyFirstLaneUsed(const VPValue *Def) {
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lukel97 wrote:

We should probably rename the utils too?

https://github.com/llvm/llvm-project/pull/166562