tx_waveforms' power argument does not work correctly with all channels

[joelkeeling]

Issue Description

The example program tx_waveforms does not properly handle the power argument with all channels

Setup Details

Run the example program with the '--power' argument AND set the '--channels' argument to any valid channel besides '0'

Expected Behavior

The power would be correctly configured for the specific channel(s)

Actual Behaviour

Configuration settings get written to the incorrect channel(s)

Steps to reproduce the problem

I will instead describe the fix to the problem:
There is an error in the set_tx_power_reference call, ch should actually be channel_nums[ch]

Additional Information

We have corrected this issue on our local system. If time permits, I hope to provide a small Pull Request to correct the issue.

[manderseck]

Thanks for reporting and fixing these issues. Your changes have been merged into our internal master and will be publicly available with the next push to the public uhd repo.