leds: leds-lm3530: Fix incorrect spelling of 'brightness'

Fixes the following W=1 kernel build warning(s):

 drivers/leds/leds-lm3530.c:113: warning: Function parameter or member 'brightness' not described in 'lm3530_data'

Cc: Pavel Machek <pavel@ucw.cz>
Cc: Kumar SAHU <shreshthakumar.sahu@stericsson.com>
Cc: Dan Murphy <D.Murphy@motorola.com>
Cc: linux-leds@vger.kernel.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Pavel Machek <pavel@ucw.cz>

drivers/leds/leds-lm3530.c

@@ -99,7 +99,7 @@ static struct lm3530_mode_map mode_map[] = {
  * @pdata: LM3530 platform data
  * @mode: mode of operation - manual, ALS, PWM
  * @regulator: regulator
- * @brighness: previous brightness value
+ * @brightness: previous brightness value
  * @enable: regulator is enabled
  */
 struct lm3530_data {