[review] LTE attach config/status support

[Aleksander Morgado]

Hey,

The following MR implements support for the LTE attach config/status
operations described in the "Microsoft Basic Connect Extensions"
service (*):
https://gitlab.freedesktop.org/mobile-broadband/libmbim/merge_requests/5

I didn't implement the Set operation via mbimcli for the Config
method, as I'd like to do that directly in MM as a new API.

Comments/review welcome!

(*) https://docs.microsoft.com/en-us/windows-hardware/drivers/network/mb-lte-attach-operations

-- 
Aleksander
https://aleksander.es