Fixed errors in GPS data definitions.

* Fixed incorrect order of unk0 & data_available fields.
* Fixed misspellings.
* Many fields are actually arrays (this was causing a lot of fields to
have nonsense values).

Based on https://github.com/paparazzi/paparazzi/blob/55e3d9d79119f81ed0b11a59487280becf13cf40/sw/airborne/boards/ardrone/at_com.h