[dv] get ibex dv co-sim to run w questa
[dv] get ibex dv co-sim to run w questa

This resolves lowRISC/Ibex#1280.

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