SITL: Adding Swift Binary Protocol GPS type

libraries/SITL/SITL.h

@@ -39,7 +39,8 @@ public:
         GPS_TYPE_MTK   = 2,
         GPS_TYPE_MTK16 = 3,
         GPS_TYPE_MTK19 = 4,
-        GPS_TYPE_NMEA  = 5
+        GPS_TYPE_NMEA  = 5,
+        GPS_TYPE_SBP   = 6
     };
 
 	struct sitl_fdm state;