try using gpio_test example. it includes a saimple gpio kernel module. Run it with default settings first, then change LED_GPIO in source code whatever NS9210 GPIO you want to control
#define GPIO_PIN_DEVICE_BUT "/dev/gpio/1"
#define GPIO_PIN_DEVICE_LED "/dev/gpio/2"
Looking at module schematics the Activity LED is NS9210 pin E15 (not F15 as I previously thought, sorry for the confusion) So it should be GPIO or /dev/gpio/9