leds: mlxreg: Fix possible buffer overflow

Error was detected by PVS-Studio:
V512 A call of the 'sprintf' function will lead to overflow of
the buffer 'led_data->led_cdev_name'.

Acked-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Oleh Kravchenko <oleg@kaa.org.ua>
Signed-off-by: Pavel Machek <pavel@ucw.cz>

drivers/leds/leds-mlxreg.c

@@ -228,8 +228,8 @@ static int mlxreg_led_config(struct mlxreg_led_priv_data *priv)
 			brightness = LED_OFF;
 			led_data->base_color = MLXREG_LED_GREEN_SOLID;
 		}
-		sprintf(led_data->led_cdev_name, "%s:%s", "mlxreg",
-			data->label);
+		snprintf(led_data->led_cdev_name, sizeof(led_data->led_cdev_name),
+			 "mlxreg:%s", data->label);
 		led_cdev->name = led_data->led_cdev_name;
 		led_cdev->brightness = brightness;
 		led_cdev->max_brightness = LED_ON;