message: [XLA] Update InstructionFusion::EffectivelyAtMostUnary for kIota
  It should behave like kBroadcast with respect to it being "effectively unary."
diff: @@ -172,7 +172,8 @@ bool InstructionFusion::EffectivelyAtMostUnary(HloInstruction* hlo) {
  });
  return std::count_if(hlo->operands().begin(), hlo->operands().end(),
  [output_rank](HloInstruction* operand) {
  - if (operand->opcode() == HloOpcode::kBroadcast) {
  + if (operand->opcode() == HloOpcode::kBroadcast ||
  + operand->opcode() == HloOpcode::kIota) {
  return false;
  }
  if (operand->opcode() == HloOpcode::kConstant &&
  