opt_lut: simplify type conversion. NFC.
opt_lut: simplify type conversion. NFC.

SymbiFlow/yosys,cliffordwolf/yosys,antmicro/yosys,SymbiFlow/yosys,SymbiFlow/yosys,SymbiFlow/yosys,SymbiFlow/yosys,cliffordwolf/yosys,YosysHQ/yosys,cliffordwolf/yosys,YosysHQ/yosys,antmicro/yosys,antmicro/yosys,antmicro/yosys,cliffordwolf/yosys,antmicro/yosys,YosysHQ/yosys,YosysHQ/yosys,cliffordwolf/yosys,YosysHQ/yosys,cliffordwolf/yosys,YosysHQ/yosys,antmicro/yosys,YosysHQ/yosys,YosysHQ/yosys,antmicro/yosys,cliffordwolf/yosys,SymbiFlow/yosys,cliffordwolf/yosys,SymbiFlow/yosys,cliffordwolf/yosys,antmicro/yosys,SymbiFlow/yosys