[jtag,dv] Get rid of exit_to_rti_dr_past

[rswarbrick]

I'm pretty certain that the author wasn't quite modelling the current TAP FSM state properly and the naming is rather confusing.

I think the name is probably backwards and the variable being set means that we think we're in the Test-Logic-Reset state instead of Run-Test/Idle. But it isn't actually always correct (and the name is confusing). Drop it. If necessary, we can follow up by tracking things more explictly.