[VPlan] Use early exit in ::extractLastLaneOfFirstOperand (NFC).

Reduce indent level, as suggested in
#136455.

Author: fhahn

llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp

@@ -1142,14 +1142,14 @@ void VPIRInstruction::extractLastLaneOfFirstOperand(VPBuilder &Builder) {
          "can only update exiting operands to phi nodes");
   assert(getNumOperands() > 0 && "must have at least one operand");
   VPValue *Exiting = getOperand(0);
-  if (!Exiting->isLiveIn()) {
-    LLVMContext &Ctx = getInstruction().getContext();
-    auto &Plan = *getParent()->getPlan();
-    Exiting = Builder.createNaryOp(
-        VPInstruction::ExtractFromEnd,
-        {Exiting,
-         Plan.getOrAddLiveIn(ConstantInt::get(IntegerType::get(Ctx, 32), 1))});
-  }
+  if (Exiting->isLiveIn())
+    return;
+
+  LLVMContext &Ctx = getInstruction().getContext();
+  auto &Plan = *getParent()->getPlan();
+  Exiting = Builder.createNaryOp(VPInstruction::ExtractFromEnd,
+                                 {Exiting, Plan.getOrAddLiveIn(ConstantInt::get(
+                                               IntegerType::get(Ctx, 32), 1))});
   setOperand(0, Exiting);
 }