opt_dff: With -keepdc, never turn undef init vals into const drivers
opt_dff: With -keepdc, never turn undef init vals into const drivers

YosysHQ/yosys,YosysHQ/yosys,YosysHQ/yosys,YosysHQ/yosys,YosysHQ/yosys,YosysHQ/yosys,YosysHQ/yosys,YosysHQ/yosys