Apparently it's not legal to create a QMI service multiple times for
a device. I've been testing with a Quectel EC21 and here it works fine
to do so, but the general case would require "shared" services across
atoms.
This patch switches the users of the NAS and WDS services over to using
a "shared" service instead of each instatiating their own instance.
Calling the ps_state/cs_state alternatives *ATTACH_STATUS* was confusing
because there is also a status field in the *serving_system structure.
This patch does a minor rename and adds the appropriate definitions for
the status field.
LTE modems (observed with Telit LE910 V1) can power on
already registered to a network. In that case, the SS_INFO
change notification will never arrive, and the gprs driver
will never be marked as attached.
To avoid this situation, read SS_INFO at probe time, and if
registered, mark the gprs driver as attached.