arith_map: add carry_cout also for lcu
arith_map: add carry_cout also for lcu

Signed-off-by: Alessandro Comodi <622632e70fd6771cf2cd943f69e5e51ab66adef8@antmicro.com>

SymbiFlow/yosys,SymbiFlow/yosys,SymbiFlow/yosys,SymbiFlow/yosys,SymbiFlow/yosys,SymbiFlow/yosys,SymbiFlow/yosys,SymbiFlow/yosys