base-modem: trigger full modem reprobe on new port notifications

If we have a valid modem object created and we receive a notification for a new port during runtime, it may very likely mean that we created the modem object too soon, without the full list of ports that the device exposes.

Instead of going on with the incomplete modem object, trigger a full reprobe right away so that we are sure we use all the available ports.

This is specially important if the port being reported is e.g. a QMI or MBIM control port, we don't want to ignore those as it could mean we're falling back to AT+PPP when it's not really mandatory to do so.