(try to) enable interrupts for the aDIO gatevalve control.

We need to be more aware of the state of the gatevalve interlock. As it stands if the interlock blocks the gatevalve open signal (thus closing it), then later unblocks it, the gatevalve will reopen. We want the interlock blocking to latch.

More specifically, the interlock circuit can be powered down or jumpered off, which then closes the valve. Good. But if the valve is closed that way, the aDIO driver on the BEE is still requesting that the valve be open. So if later the interlock circuit is powered back up, or the jumper reinstalled, the valve immediately opens. Scary.

JHU might change the circuit. But I'd like the XCU to be more conservative. The (C) aDIO driver from RTD supports interrupts; I'd like to have that trigger our gatevalve control to retire the open request.