add macro PX4FMU_TASK to board_config

src/drivers/boards/auav-x21/board_config.h

@@ -211,6 +211,9 @@
 
 #define BOARD_NAME "AUAV_X21"
 
+// Run the FMU task on its own thread to reduce jitter
+#define PX4FMU_TASK
+
 /* By Providing BOARD_ADC_USB_CONNECTED this board support the ADC
  * system_power interface, and therefore provides the true logic
  * GPIO BOARD_ADC_xxxx macros.

src/drivers/boards/px4fmu-v4/board_config.h

@@ -275,6 +275,9 @@
 
 #define	BOARD_NAME "PX4FMU_V4"
 
+// Run the FMU task on its own thread to reduce jitter
+#define PX4FMU_TASK
+
 /* By Providing BOARD_ADC_USB_CONNECTED (using the px4_arch abstraction)
  * this board support the ADC system_power interface, and therefore
  * provides the true logic GPIO BOARD_ADC_xxxx macros.