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'
0436b3e457