drivers/uavcan: GNSS set system time based on fix_type instead of val…

…id_pos_cov

src/drivers/uavcan/sensors/gnss.cpp

@@ -436,7 +436,7 @@ void UavcanGnssBridge::process_fixx(const uavcan::ReceivedDataStructure<FixType>
 	}
 
 	// If we haven't already done so, set the system clock using GPS data
-	if (valid_pos_cov && !_system_clock_set) {
+	if ((fix_type >= sensor_gps_s::FIX_TYPE_2D) && !_system_clock_set) {
 		timespec ts{};
 
 		// get the whole microseconds