nmea_gps: Handle different GGA structure
nmea_gps: Handle different GGA structure

Testing against ublox - handle null age of differential GPS.

Signed-off-by: Noel Eck <1e36ab6ededef40f3f16bdbc1b09eee72c5d08cf@intel.com>

g-vidal/upm,Propanu/upm,Propanu/upm,Propanu/upm,g-vidal/upm,stefan-andritoiu/upm,stefan-andritoiu/upm,stefan-andritoiu/upm,intel-iot-devkit/upm,Propanu/upm,Propanu/upm,stefan-andritoiu/upm,g-vidal/upm,g-vidal/upm,intel-iot-devkit/upm,intel-iot-devkit/upm,stefan-andritoiu/upm,intel-iot-devkit/upm,g-vidal/upm,intel-iot-devkit/upm,intel-iot-devkit/upm,Propanu/upm,stefan-andritoiu/upm,g-vidal/upm