leds: Standardise LED naming scheme

As discussed on LKML some notion of 'function' is needed in
LED naming. This patch adds this to the documentation and
standardises existing LED drivers.

Signed-off-by: Richard Purdie <rpurdie@rpsys.net>
diff --git a/drivers/hwmon/applesmc.c b/drivers/hwmon/applesmc.c
index 86c66c3..0c94770 100644
--- a/drivers/hwmon/applesmc.c
+++ b/drivers/hwmon/applesmc.c
@@ -905,7 +905,7 @@
 }
 
 static struct led_classdev applesmc_backlight = {
-	.name			= "smc:kbd_backlight",
+	.name			= "smc::kbd_backlight",
 	.default_trigger	= "nand-disk",
 	.brightness_set		= applesmc_brightness_set,
 };