fix the wrong ADC_channel names in LFP canvas

The wrong ADC_channel names bug: The ADC channels are given names of "AUX" in LFP viewer.
before ADC channels being enabled: 
![image](https://cloud.githubusercontent.com/assets/7818495/5543989/6bc501aa-8acb-11e4-920b-1cf9896fa0fb.png)

after ADC channels being enabled:
![image](https://cloud.githubusercontent.com/assets/7818495/5543985/5c56bfc4-8acb-11e4-85c7-a3c1da6137bd.png)