leds: save the delay values after a successful call to blink_set()

When calling the hardware blinking function implemented by blink_set(),
the delay_on and delay_off values are not preserved across calls.

Fix that and make the "timer" trigger work as expected when hardware
blinking is available.

BEFORE the fix:
  $ cd /sys/class/leds/someled
  $ echo timer > trigger
  $ cat delay_on delay_off
  0
  0
  $ echo 100 > delay_on
  $ cat delay_on delay_off
  0
  0
  $ echo 100 > delay_off
  $ cat delay_on delay_off
  0
  0

AFTER the fix:
  $ cd /sys/class/leds/someled
  $ echo timer > trigger
  $ cat delay_on delay_off
  0
  0
  $ echo 100 > delay_on
  $ cat delay_on delay_off
  100
  0
  $ echo 100 > delay_off
  $ cat delay_on delay_off
  100
  100

Signed-off-by: Antonio Ospite <ospite@studenti.unina.it>
Reviewed-by: Johannes Berg <johannes@sipsolutions.net>
Cc: Richard Purdie <rpurdie@rpsys.net>
Cc: <stable@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/leds/led-class.c

@@ -268,8 +268,11 @@ void led_blink_set(struct led_classdev *led_cdev,
 		   unsigned long *delay_off)
 {
 	if (led_cdev->blink_set &&
-	    !led_cdev->blink_set(led_cdev, delay_on, delay_off))
+	    !led_cdev->blink_set(led_cdev, delay_on, delay_off)) {
+		led_cdev->blink_delay_on = *delay_on;
+		led_cdev->blink_delay_off = *delay_off;
 		return;
+	}
 
 	/* blink with 1 Hz as default if nothing specified */
 	if (!*delay_on && !*delay_off)