[ARM] Change getScalarizationOverhead overload used in gather costs. NFC

This changes which of the getScalarizationOverhead overloads is used in
the gather/scatter cost to use the base variant directly, not relying on
the version using heuristics on the number of args with no args
provided. It should still produce the same costs for scalarized
gathers/scatters.

Author: davemgreen

llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp

@@ -1416,8 +1416,9 @@ unsigned ARMTTIImpl::getGatherScatterOpCost(unsigned Opcode, Type *DataTy,
   unsigned VectorCost = NumElems * LT.first * ST->getMVEVectorCostFactor();
   // The scalarization cost should be a lot higher. We use the number of vector
   // elements plus the scalarization overhead.
-  unsigned ScalarCost =
-      NumElems * LT.first + BaseT::getScalarizationOverhead(VTy, {});
+  unsigned ScalarCost = NumElems * LT.first +
+                        BaseT::getScalarizationOverhead(VTy, true, false) +
+                        BaseT::getScalarizationOverhead(VTy, false, true);
 
   if (EltSize < 8 || Alignment < EltSize / 8)
     return ScalarCost;