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/leds/leds-wrap.c b/drivers/leds/leds-wrap.c
index 27fb2d8..5770cc3 100644
--- a/drivers/leds/leds-wrap.c
+++ b/drivers/leds/leds-wrap.c
@@ -43,12 +43,12 @@
 }
 
 static struct led_classdev wrap_error_led = {
-	.name		= "wrap:error",
+	.name		= "wrap::error",
 	.brightness_set	= wrap_error_led_set,
 };
 
 static struct led_classdev wrap_extra_led = {
-	.name           = "wrap:extra",
+	.name           = "wrap::extra",
 	.brightness_set = wrap_extra_led_set,
 };