Modify board_power_off() so that is is called only via boardctl()

system/poweroff/Kconfig

@@ -6,6 +6,8 @@
 config SYSTEM_POWEROFF
 	bool "Power-Off"
 	default n
+	depends on LIB_BOARDCTL
+	select BOARDCTL_POWEROFF
 	---help---
 		Enable support for the NSH poweroff command.  NOTE: This option
 		provides the NSH power-off command only.  It requires board-specific

system/poweroff/poweroff.c

@@ -37,7 +37,7 @@
  * Included Files
  ****************************************************************************/
 
-#include <nuttx/board.h>
+#include <sys/boardctl.h>
 
 /****************************************************************************
  * Public Functions
@@ -49,24 +49,10 @@ int main(int argc, FAR char *argv[])
 int poweroff_main(int argc, char *argv[])
 #endif
 {
-  /* TODO:
+  /* Invoide the BOARDIOC_POWEROFF board control to shutdown the board 
-   *  - replace this by sending general system signal to shutdown, where i.e. nsh
+   * If board_power_off function returns, then it was not possible to power-off the
-   *    must issue down script (it may check whether nsh is running before spawning
-   *    a new process with nsh poweroff)
-   *  - wait for some time (~0.5 second for VSN), that SDcard is flashed and synced
-   *  - call poweroff
-   *
-   * TODO on boot:
-   *  - if external key is pressed, do not start the nsh! but wait until it is released
-   *    (to get rid of bad mounts of the sdcard etc.) this could be handled in the
-   *    button driver immediately on system boot
-   */
-
-  board_power_off();
-
-  /* If board_power_off function returns, then it was not possible to power-off the
    * board due to some constraints.
    */
 
-  return 0;
+  return boardctl(BOARDIOC_POWEROFF, 0);
 }