I want to control the two LED's (LED400 and LED401) on the Artik 710 development board through the Sys interface. To accomplish it, I modified the dtsi file of Artik710 in the Linux kernel. However, after building the image and booting the board, the LED's do not appear in the /sys/class directory. My code in the dtsi file is as follows

```
    gpio-leds {
            compatible = "gpio-leds";

            Blue {
                    label = "Blue";
                    gpios = <&gpio_a 28 0>;
                    linux,default-trigger = "heartbeat";
                    linux,default-state = "on";
            };

            Red {
                    label = "Red";
                    gpios = <&gpio_b 6 0>;
                    linux,default-trigger = "heartbeat";
                    linux,default-state = "on";
            };

    };

```

Can someone point the issue here?