If the modem supports ^SIND psinfo reporting, we enable the URC and
flag the access technology polling unsupported, so that we only update
access technology via the +CIEV URCs.
E.g.:
(ttyACM1): --> 'AT^SIND="psinfo",1<CR>'
(ttyACM1): <-- '<CR><LF>^SIND: psinfo,1,10<CR><LF><CR><LF>OK<CR><LF>'
Reporting initial access technologies...
Modem /org/freedesktop/ModemManager1/Modem/0: access technology changed (unknown -> hsdpa, hsupa)
...
(ttyACM1): <-- '<CR><LF>+CIEV: psinfo,4<CR><LF>'
Modem /org/freedesktop/ModemManager1/Modem/0: access technology changed (hsdpa, hsupa -> edge)
...
f4c4e36461