We'll try to cope with getting devices being reported in either 'usb' or
'usbmisc', trying to avoid the need of checking kernel version during runtime.
Different ports of the same modem may get handled by different drivers. We
therefore need to provide a list of drivers (new `Modem.Drivers' property with
signature 'as') instead of just one (removed `Modem.Driver' property with
signature 's').
$ sudo mmcli -m 0 | grep drivers
| drivers: 'qcserial, qmi_wwan'
Before this, we only exported the modem to DBus when all ports were organized,
in order to make sure that we select as primary port the one we really want and
not the first AT port grabbed. Given that to get all the ports organized we also
needed to wait to get all the ports grabbed, we can now also defer the creation
of the modem object until all the ports get grabbed. This allows us to create
different types of objects based on the ports available (e.g. we can now create
QMI-supported modem objects if we see a QMI port around).