Add support for benchmarking multi-channel streamers. This also
simplifies the way the test parameters are specified to avoid confusion
due to the additional dimension. For rx, multi-channel streamer
configurations require split_stream noc blocks so that timestamps of
packets in the same streamer align. Add support for loopback FIFOs.
This makes the noc traffic counter register actually reflect the
registers in the FPGA. The FPGA register names were changed prior to
merging to master, and the ready count registers were removed.
