Draft: executor/pdu: devantech: Fix off-by-one

From the docs: Digital Active - follow with 1-8 to set relay on, then a time for pulsed output from 1-255 (100ms resolution) or 0 for permanent. Board will return 0 for success, 1 for failure

Intern our ports are starting from zero - use port_id + 1 for the request.

Signed-off-by: Christian Gmeiner cgmeiner@igalia.com