leds: core: fix misleading comment after workqueue removal from drivers

Now that workqueues have been removed from individual drivers and
were replaced with a core-internal workqueue we shouldn't
encourage people to add new workqueues to drivers.
Signed-off-by: NHeiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: NJacek Anaszewski <j.anaszewski@samsung.com>

include/linux/leds.h

@@ -49,8 +49,10 @@ struct led_classdev {
 #define LED_SYSFS_DISABLE	(1 << 22)
 #define LED_DEV_CAP_FLASH	(1 << 23)
 
-	/* Set LED brightness level */
-	/* Must not sleep, use a workqueue if needed */
+	/* Set LED brightness level
+	 * Must not sleep. Use brightness_set_blocking for drivers
+	 * that can sleep while setting brightness.
+	 */
 	void		(*brightness_set)(struct led_classdev *led_cdev,
 					  enum led_brightness brightness);
 	/*