Look up devices by ID and not by name

[dNechita]

When constructing the devices and channels tree in 'Capture Window', lookup for devices by ID and not by name. This prevents issues in scenarios where multiple devices exist and have the same name. Otherwise all channels from all devices will be placed under the first device leaving the rest of devices with no channels.

Also see: https://ez.analog.com/sw-interface-tools/f/q-a/519863/iio-oscilloscope-plot-channel-display-issue-with-multiple-ad4020-devices

[rgetz]

could do the same by label - I can bump this up on the libiio list if you need.

[dNechita]

I think the ID is sufficient.