Move member from obd2_signals_t class to

Move member from obd2_signals_t class to
active_diagnostic_request_t (adr)class. It's more logical
to have them here as call about incoming diagnostic CAN
messages are made against adr class not obd2_signal_t that
it's a subset of diagnostic messages.

It's made to handle obd2 requests as well as normal UDS
diagnostic request for constructor proprietary diagnostic
signals.

Change-Id: I96c714640d6ecfa25dfc9942974057c1797eb0e1
Signed-off-by: Romain Forlot <romain.forlot@iot.bzh>