leds: Further document parameters for blink_set()

The documentation for the parameters of blink_set() was a bit hard
to find so put some where I'd expected to find it.
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Richard Purdie <rpurdie@linux.intel.com>

include/linux/leds.h

@@ -45,7 +45,9 @@ struct led_classdev {
 	/* Get LED brightness level */
 	enum led_brightness (*brightness_get)(struct led_classdev *led_cdev);
 
-	/* Activate hardware accelerated blink */
+	/* Activate hardware accelerated blink, delays are in
+	 * miliseconds and if none is provided then a sensible default
+	 * should be chosen. */
 	int		(*blink_set)(struct led_classdev *led_cdev,
 				     unsigned long *delay_on,
 				     unsigned long *delay_off);