cinterion: support AT^SGPSC capable modems

The AT^SGPSS command provides an easy way to just start/stop GPS, but
unfortunately it isn't supported by all Cinterion modems.

The AT^SGPSC command instead is more widely available but it requires
several steps to start and stop the different elements of the GPS
receiver.

Implement support for both, preferring AT^SGPSSS if available and
falling back to AT^SGPSC otherwise.
1 file changed