Enabling GPS support for the Cinterion PLS8 devices

[Aleksander Morgado]

Hey Dan, Matthew & everyone,

The following patches implement support for GPS capabilities in the Cinterion PLS8-X, PLS8-E and similar devices, plus some additional improvements in how GPS support is handled.

The logic is based on Matthew's original logic included in the patch he submitted here:
https://lists.freedesktop.org/archives/modemmanager-devel/2016-August/003381.html

Comments?

[PATCH 1/5] cinterion,location: refactor enable/disable and
[PATCH 2/5] cinterion: flag PLS8 GPS data port
[PATCH 3/5] cinterion: setup GPS port only if GPS support detected
[PATCH 4/5] cinterion: support AT^SGPSC capable modems
[PATCH 5/5] cinterion: retry GPS Engine activation up to 3 times