FMUv2: Save 3KB of RAM

src/drivers/boards/px4fmu-v2/board_config.h

@@ -1,6 +1,6 @@
 /****************************************************************************
  *
- *   Copyright (c) 2013, 2014 PX4 Development Team. All rights reserved.
+ *   Copyright (c) 2013-2016 PX4 Development Team. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -272,7 +272,7 @@ __BEGIN_DECLS
 
 /* This board provides a DMA pool and APIs */
 
-#define BOARD_DMA_ALLOC_POOL_SIZE 8192
+#define BOARD_DMA_ALLOC_POOL_SIZE 5120
 /****************************************************************************************************
  * Public Types
  ****************************************************************************************************/