RUI ADC Initialize

RUI_RETURN_STATUS rui_adc_init(RUI_GPIO_ST *rui_gpio);

@brief	This API is used to initialize ADC
@return	RUI_RETURN_STATUS
@param	RUI_GPIO_ST *rui_gpio: the instance of GPIO.
@module	RAK811, RAK4200, RAK4400, RAK4600, RAK5010 and RAK8212-M.