make userleds work on Arduino Due

- makes the 'leds' example command work:
  - adds code to initialize the /dev/userleds device
  - adds defconfig and docs

boards/arm/sam34/arduino-due/README.txt

@@ -861,3 +861,9 @@ Configuration sub-directories
 
        STATUS:
        2013-7-2:  TSC is not responding.  All 0's received on SPI.
+
+  nsh-leds:
+    This configuration directory will build the NuttX Shell and enable the user
+    LEDS (/dev/userleds). It will also enable the LED example program (leds).
+    Running the leds command will start up an LED daemon which will light up the 
+    L (user), TX, and RX LEDs in a binary sequence. 

boards/arm/sam34/arduino-due/configs/nsh-leds/defconfig

@@ -0,0 +1,47 @@
+#
+# This file is autogenerated: PLEASE DO NOT EDIT IT.
+#
+# You can use "make menuconfig" to make any modifications to the installed .config file.
+# You can then do "make savedefconfig" to generate a new defconfig file that includes your
+# modifications.
+#
+# CONFIG_ARCH_LEDS is not set
+# CONFIG_ARCH_RAMFUNCS is not set
+# CONFIG_READLINE_ECHO is not set
+CONFIG_ARCH="arm"
+CONFIG_ARCH_BOARD="arduino-due"
+CONFIG_ARCH_BOARD_ARDUINO_DUE=y
+CONFIG_ARCH_CHIP="sam34"
+CONFIG_ARCH_CHIP_ATSAM3X8E=y
+CONFIG_ARCH_CHIP_SAM34=y
+CONFIG_ARCH_CHIP_SAM3X=y
+CONFIG_ARCH_STACKDUMP=y
+CONFIG_BOARD_LATE_INITIALIZE=y
+CONFIG_BOARD_LOOPSPERMSEC=6965
+CONFIG_BUILTIN=y
+CONFIG_DEV_ZERO=y
+CONFIG_EXAMPLES_LEDS=y
+CONFIG_FS_PROCFS=y
+CONFIG_HAVE_CXX=y
+CONFIG_HAVE_CXXINITIALIZE=y
+CONFIG_INIT_ENTRYPOINT="nsh_main"
+CONFIG_MM_REGIONS=3
+CONFIG_NSH_ARCHINIT=y
+CONFIG_NSH_BUILTIN_APPS=y
+CONFIG_NSH_DISABLE_IFUPDOWN=y
+CONFIG_NSH_FILEIOSIZE=512
+CONFIG_NSH_READLINE=y
+CONFIG_PREALLOC_TIMERS=4
+CONFIG_RAM_SIZE=65536
+CONFIG_RAM_START=0x20000000
+CONFIG_RAW_BINARY=y
+CONFIG_RR_INTERVAL=200
+CONFIG_SCHED_WAITPID=y
+CONFIG_START_DAY=28
+CONFIG_START_MONTH=6
+CONFIG_START_YEAR=2013
+CONFIG_SYSTEM_NSH=y
+CONFIG_TASK_NAME_SIZE=32
+CONFIG_UART0_SERIAL_CONSOLE=y
+CONFIG_USERLED=y
+CONFIG_USERLED_LOWER=y

boards/arm/sam34/arduino-due/include/board.h

@@ -147,6 +147,8 @@
  * GPIO output to low.
  */
 
+#define LED_DRIVER_PATH "/dev/userleds"
+
 /* LED index values for use with board_userled() */
 
 #define BOARD_LED_L       0

boards/arm/sam34/arduino-due/src/sam_boot.c

@@ -74,4 +74,5 @@ void board_late_initialize(void)
 
   sam_bringup();
 }
+
 #endif

boards/arm/sam34/arduino-due/src/sam_bringup.c

@@ -29,13 +29,22 @@
 
 #include <nuttx/board.h>
 #include <nuttx/fs/fs.h>
+#include <nuttx/leds/userled.h>
 
 #include "arduino-due.h"
 
+#include <arch/board/board.h>
+
 /****************************************************************************
  * Pre-processor Definitions
  ****************************************************************************/
 
+#undef HAVE_LEDS
+
+#if !defined(CONFIG_ARCH_LEDS) && defined(CONFIG_USERLED_LOWER)
+#  define HAVE_LEDS 1
+#endif
+
 #if defined(CONFIG_ARDUINO_ITHEAD_TFT) && defined(CONFIG_SPI_BITBANG) && \
     defined(CONFIG_MMCSD_SPI)
 
@@ -116,6 +125,19 @@ int sam_bringup(void)
     }
 #endif
 
+#ifdef HAVE_LEDS
+  board_userled_initialize();
+
+  /* Register the LED driver */
+
+  ret = userled_lower_initialize(LED_DRIVER_PATH);
+  if (ret < 0)
+    {
+      syslog(LOG_ERR, "ERROR: userled_lower_initialize() failed: %d\n", ret);
+      return ret;
+    }
+#endif
+
   UNUSED(ret);
   return OK;
 }

boards/arm/sam34/arduino-due/src/sam_userleds.c

@@ -28,12 +28,12 @@
 #include <stdbool.h>
 #include <debug.h>
 
-#include <arch/board/board.h>
-
 #include "chip.h"
 #include "sam_gpio.h"
 #include "arduino-due.h"
 
+#include <arch/board/board.h>
+
 #ifndef CONFIG_ARCH_LEDS
 
 /****************************************************************************