[VPlan] Treat VPVector(End)PointerRecipe as single-scalar, if ops are.

VPVector(End)PointerRecipes are single-scalar if all their operands are.
This should be effectively NFC currently, but it should re-enable cost
checking for some more VPWidenMemoryRecipe after
#157387 as discovered by
@john-brawn-arm.

Author: fhahn

llvm/lib/Transforms/Vectorize/VPlanUtils.cpp

@@ -185,7 +185,8 @@ bool vputils::isSingleScalar(const VPValue *VPV) {
                                      all_of(Rep->operands(), isSingleScalar));
   }
   if (isa<VPWidenGEPRecipe, VPDerivedIVRecipe, VPBlendRecipe,
-          VPWidenSelectRecipe>(VPV))
+          VPWidenSelectRecipe, VPVectorPointerRecipe, VPVectorEndPointerRecipe>(
+          VPV))
     return all_of(VPV->getDefiningRecipe()->operands(), isSingleScalar);
   if (auto *WidenR = dyn_cast<VPWidenRecipe>(VPV)) {
     return preservesUniformity(WidenR->getOpcode()) &&