leds: leds-mlxreg: Fix incorrect documentation of struct member 'led_cdev' and 'led_cdev_name'

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

 drivers/leds/leds-mlxreg.c:42: warning: Function parameter or member 'led_cdev' not described in 'mlxreg_led_data'
 drivers/leds/leds-mlxreg.c:42: warning: Function parameter or member 'led_cdev_name' not described in 'mlxreg_led_data'

Cc: Vadim Pasternak <vadimp@nvidia.com>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: linux-leds@vger.kernel.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Pavel Machek <pavel@ucw.cz>