leds-lp5523: set the brightness to 0 forcely on removing the driver

Turning off the brightness of each channel is required
when removing the driver.

So use flush_work() rather than cancel_work_sync() to execute
remaining brightness works.

Signed-off-by: Milo(Woogyom) Kim <milo.kim@ti.com>
Signed-off-by: Bryan Wu <bryan.wu@canonical.com>
diff --git a/drivers/leds/leds-lp5523.c b/drivers/leds/leds-lp5523.c
index 9fd9a92..2fd5689 100644
--- a/drivers/leds/leds-lp5523.c
+++ b/drivers/leds/leds-lp5523.c
@@ -974,7 +974,7 @@
 fail2:
 	for (i = 0; i < chip->num_leds; i++) {
 		led_classdev_unregister(&chip->leds[i].cdev);
-		cancel_work_sync(&chip->leds[i].brightness_work);
+		flush_work(&chip->leds[i].brightness_work);
 	}
 fail1:
 	if (pdata->enable)
@@ -993,7 +993,7 @@
 
 	for (i = 0; i < chip->num_leds; i++) {
 		led_classdev_unregister(&chip->leds[i].cdev);
-		cancel_work_sync(&chip->leds[i].brightness_work);
+		flush_work(&chip->leds[i].brightness_work);
 	}
 
 	if (chip->pdata->enable)