Add correct control of SAM power

We added a daughterboard to the BEE+SAM power brick to allow independently toggling SAM power. The control signal uses the BEE's ADIO port, which is also used to control and monitor the gatevalve. Those signals are active high: when the port is closed or the BEE powered down, the gatevalve closes.

The SAM signal is inverting: when the signal goes high the SAM power is dropped.

The issue is that the default port initialization via the kernel device and our cython shim seems to drop SAM power. This is a bit surprising, hence this ticket.