Merge pull request analogdevicesinc#348 from mphalke/ad7689-minor-update

ad7689: Corrected the 'channels' attribute name

adi/ad7689.py

@@ -73,7 +73,7 @@ def __init__(self, uri="", device_name=""):
                 self._rxadc = device
                 break
 
-        for ch in self._ctrl._channels:
+        for ch in self._ctrl.channels:
             name = ch._id
             self._rx_channel_names.append(name)
             self.channel.append(self._channel(self._ctrl, name))