[VPlan] Remove unneeded VPValue::getLiveInIRValue() const (NFC).

The accessor is not needed/used.

Author: fhahn

llvm/lib/Transforms/Vectorize/VPlanValue.h

@@ -175,12 +175,7 @@ class VPValue {
   /// Returns the underlying IR value, if this VPValue is defined outside the
   /// scope of VPlan. Returns nullptr if the VPValue is defined by a VPDef
   /// inside a VPlan.
-  Value *getLiveInIRValue() {
-    assert(isLiveIn() &&
-           "VPValue is not a live-in; it is defined by a VPDef inside a VPlan");
-    return getUnderlyingValue();
-  }
-  const Value *getLiveInIRValue() const {
+  Value *getLiveInIRValue() const {
     assert(isLiveIn() &&
            "VPValue is not a live-in; it is defined by a VPDef inside a VPlan");
     return getUnderlyingValue();