Simple System: Correctly tie-off unused signals
Simple System: Correctly tie-off unused signals

Two unused bits of device_err were only assigned in an initial block,
and it not in Verilator. They should have been tied off always to avoid
mixed blocking/nonblocking assignments to the same signal.

AmbiML/ibex,AmbiML/ibex,AmbiML/ibex,lowRISC/ibex,lowRISC/ibex,AmbiML/ibex,lowRISC/ibex,lowRISC/ibex