esp8266: Link ADC class into machine module.
diff --git a/esp8266/modmachine.c b/esp8266/modmachine.c
index 817b5a2..5cf6f58 100644
--- a/esp8266/modmachine.c
+++ b/esp8266/modmachine.c
@@ -143,6 +143,7 @@
{ MP_ROM_QSTR(MP_QSTR_Timer), MP_ROM_PTR(&esp_timer_type) },
{ MP_ROM_QSTR(MP_QSTR_Pin), MP_ROM_PTR(&pyb_pin_type) },
{ MP_ROM_QSTR(MP_QSTR_PWM), MP_ROM_PTR(&pyb_pwm_type) },
+ { MP_ROM_QSTR(MP_QSTR_ADC), MP_ROM_PTR(&pyb_adc_type) },
{ MP_ROM_QSTR(MP_QSTR_I2C), MP_ROM_PTR(&pyb_i2c_type) },
{ MP_ROM_QSTR(MP_QSTR_SPI), MP_ROM_PTR(&pyb_spi_type) },
};