leds: leds-lm3692x: Fix some kernel-doc formatting issues

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

 drivers/leds/leds-lm3692x.c:121: warning: Function parameter or member 'lock' not described in 'lm3692x_led'
 drivers/leds/leds-lm3692x.c:121: warning: Function parameter or member 'client' not described in 'lm3692x_led'
 drivers/leds/leds-lm3692x.c:121: warning: Function parameter or member 'led_dev' not described in 'lm3692x_led'
 drivers/leds/leds-lm3692x.c:121: warning: Function parameter or member 'regmap' not described in 'lm3692x_led'
 drivers/leds/leds-lm3692x.c:121: warning: Function parameter or member 'enable_gpio' not described in 'lm3692x_led'
 drivers/leds/leds-lm3692x.c:121: warning: Function parameter or member 'regulator' not described in 'lm3692x_led'
 drivers/leds/leds-lm3692x.c:121: warning: Function parameter or member 'led_enable' not described in 'lm3692x_led'
 drivers/leds/leds-lm3692x.c:121: warning: Function parameter or member 'model_id' not described in 'lm3692x_led'
 drivers/leds/leds-lm3692x.c:121: warning: Function parameter or member 'boost_ctrl' not described in 'lm3692x_led'
 drivers/leds/leds-lm3692x.c:121: warning: Function parameter or member 'brightness_ctrl' not described in 'lm3692x_led'
 drivers/leds/leds-lm3692x.c:121: warning: Function parameter or member 'enabled' not described in 'lm3692x_led'

Cc: Pavel Machek <pavel@ucw.cz>
Cc: Liam Girdwood <lgirdwood@gmail.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Dan Murphy <dmurphy@ti.com>
Cc: linux-leds@vger.kernel.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Pavel Machek <pavel@ucw.cz>