[SRU] Patches needed for Telit modems used in IOT systems

[Anthony Wong]

We have been informed by Telit that additional patches are required to enable their WWAN modems. Those patches are already upstreamed in modemmanager but not yet in Xenial.

[Impact]
Since this device is needed for 16.04 project, we need SRU for modemmanager.

The patches are:

* telit: add modem_power_down to telit plugin
commit: 14e47710561b2021b79814afa5ecd6b2abc4fad0
This patch implements ModemManager feature set-power-state-low that is the common approach to put
the modem in +CFUN=4 state

* telit: add modem_reset to telit plugin
commit: 7978225934dc87bc74fac4d79a1080bc0501e581
This commit solves the following issue:
  The reset command (mmcli –m 0 –r) needs to tie up with the AT command (AT#REBOOT)

* telit: SIM unlock retries field
Main commit: c4ffe572aeeefac240f16822ca1d2d258f78ad8d
Related coding style commits: 740e1b5461bda9ff28f3ad2210ecf7238c38e785
a74edab57f53ee8c920e681145070b252f5e656e
46f601edf6046c6d6459f7aee45fca68bc93cee3
0a88ae2d6d87967c0d951cc95de0c1917c78b0ed
aae96778c54a59dcf3955c2d81bee393c0348077
This patch is necessary to fill the field “Unlock retries”, visible when mmcli -m 0 is run.

* telit: add load supported bands interface
Main commit: 70b8ec1a88477eea3a2f569a83fc270ccaff9504
Related coding style commits: 3911ea5a0f6b26e12a3586c75d72bb2c5820e3c1
This patch adds supported bands information.

* dell: fixed cgmi_retries in dell_custom_init
commit: 8a386218690aeff7e2c923a14f91da7bbc046ed2
This patch solves a random never-ending loop during port probing.

[Test Case]
We have the hardware to verify.

[Regression Potential]
By looking at those commits, they are self-contained to the telit plugin. These patches were asked by Telit to backport (we have the specification document from Telit but that's not public)

[Anthony Wong (anthonywong)]

debdiff attached.