fix carry4_cout definition
fix carry4_cout definition

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

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