[DAGCombine] Don't delete the node if it has uses immediately

This is the follow up patch for https://reviews.llvm.org/D86183 as we miss to delete the node if NegX == NegY, which has use after we create the node.
```
    if (NegX && (CostX <= CostY)) {
      Cost = std::min(CostX, CostZ);
      RemoveDeadNode(NegY);
      return DAG.getNode(Opcode, DL, VT, NegX, Y, NegZ, Flags);  #<-- NegY is used here if NegY == NegX.
    }
```

Reviewed By: spatel

Differential Revision: https://reviews.llvm.org/D86689