Revert "add macro PX4FMU_TASK to board_config"

   The fmu now support the commandline option to be run as a task
   or off a work queue.
   This reverts the board_config.h changes from commit
   e33af23122f5ee3030bb9745bbbf616b24c2a14a.

Conflicts:
	src/drivers/px4fmu/fmu.cpp

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

@@ -211,9 +211,6 @@
 
 #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

@@ -275,9 +275,6 @@
 
 #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.