[review] Use AT+CESQ for signal interface in MBIM modems if TTY available

[Aleksander Morgado]

Hey all,

This MR enables support for the "Signal" interface in MBIM modems if
they expose an AT-capable TTY port and AT+CESQ is supported. If no AT
port is available in the device, the modem will report no extended
signal capabilities, as it was doing until now for all MBIM modems.

https://gitlab.freedesktop.org/mobile-broadband/ModemManager/merge_requests/18

Comments?

-- 
Aleksander
https://aleksander.es