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 <[e-mail]>
Cc: Kumar SAHU <[e-mail]>
Cc: Dan Murphy <[e-mail]>
Cc: [e-mail]
Signed-off-by: Lee Jones <[e-mail]>
Signed-off-by: Pavel Machek <[e-mail]>

drivers/leds/leds-lm3530.c

···
  * @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 {