Status LED
  ========================================
  
  This README describes the status LED API.
  
  The API is defined by the include file include/status_led.h

  The first step is to enable CONFIG_LED_STATUS in menuconfig:
  > Device Drivers > LED Support.

  If the LED support is only for specific board, enable
  CONFIG_LED_STATUS_BOARD_SPECIFIC in the menuconfig.

  Status LEDS 0 to 5 are enabled by the following configurations at menuconfig:
  CONFIG_STATUS_LED0, CONFIG_STATUS_LED1, ... CONFIG_STATUS_LED5

  The following should be configured for each of the enabled LEDs:
  CONFIG_STATUS_LED_BIT<n>
  CONFIG_STATUS_LED_STATE<n>
  CONFIG_STATUS_LED_FREQ<n>
  Where <n> is an integer 1 through 5 (empty for 0).

  CONFIG_STATUS_LED_BIT is passed into the __led_* functions to identify which LED
  is being acted on. As such, the value choose must be unique with with respect to
  the other CONFIG_STATUS_LED_BIT's. Mapping the value to a physical LED is the

  reponsiblity of the __led_* function.

  CONFIG_STATUS_LED_STATE is the initial state of the LED. It should be set to one
  of these values: CONFIG_LED_STATUS_OFF or CONFIG_LED_STATUS_ON.

  CONFIG_STATUS_LED_FREQ determines the LED blink frequency.
  Values range from 2 to 10.

  
  Some other LED macros

  ---------------------

  CONFIG_STATUS_LED_BOOT is the LED to light when the board is booting.
  This must be a valid LED number (0-5).

  CONFIG_STATUS_LED_RED is the red LED. It is used to signal errors. This must be
  a valid LED number (0-5). Other similar color LED's macros are
  CONFIG_STATUS_LED_GREEN, CONFIG_STATUS_LED_YELLOW and CONFIG_STATUS_LED_BLUE.

  General LED functions
  ---------------------
  The following functions should be defined:

  __led_init is called once to initialize the LED to CONFIG_STATUS_LED_STATE.
  One time start up code should be placed here.

  __led_set is called to change the state of the LED.

  
  __led_toggle is called to toggle the current state of the LED.
  
  Colour LED
  ========================================

  Colour LED's are at present only used by ARM.

  
  The functions names explain their purpose.
  
  coloured_LED_init
  red_LED_on
  red_LED_off
  green_LED_on
  green_LED_off
  yellow_LED_on
  yellow_LED_off
  blue_LED_on
  blue_LED_off

  These are weakly defined in arch/arm/lib/board.c to noops. Where applicable, define

  these functions in the board specific source.
  
  TBD : Describe older board dependent macros similar to what is done for

  
  TBD : Describe general support via asm/status_led.h