[TTI] Remove getVPMemoryOpCost. NFC (llvm#160838)

No target implements this and nothing calls it. The cost of
vp.load/store/gather/scatter etc. are handled by
BasicTTIImpl::getIntrinsicInstrCost which forwards it onto the
appropriate TTI::getMemoryOpCost/getGatherScatterOpCost etc.

Author: lukel97

llvm/include/llvm/Analysis/TargetTransformInfo.h

@@ -1551,12 +1551,6 @@ class TargetTransformInfo {
       OperandValueInfo OpdInfo = {OK_AnyValue, OP_None},
       const Instruction *I = nullptr) const;
 
-  /// \return The cost of VP Load and Store instructions.
-  LLVM_ABI InstructionCost getVPMemoryOpCost(
-      unsigned Opcode, Type *Src, Align Alignment, unsigned AddressSpace,
-      TTI::TargetCostKind CostKind = TTI::TCK_RecipThroughput,
-      const Instruction *I = nullptr) const;
-
   /// \return The cost of masked Load and Store instructions.
   LLVM_ABI InstructionCost getMaskedMemoryOpCost(
       unsigned Opcode, Type *Src, Align Alignment, unsigned AddressSpace,

llvm/include/llvm/Analysis/TargetTransformInfoImpl.h

@@ -841,14 +841,6 @@ class TargetTransformInfoImplBase {
     return 1;
   }
 
-  virtual InstructionCost getVPMemoryOpCost(unsigned Opcode, Type *Src,
-                                            Align Alignment,
-                                            unsigned AddressSpace,
-                                            TTI::TargetCostKind CostKind,
-                                            const Instruction *I) const {
-    return 1;
-  }
-
   virtual InstructionCost
   getMaskedMemoryOpCost(unsigned Opcode, Type *Src, Align Alignment,
                         unsigned AddressSpace,