Support for TM3/TM4 in srsRAN_4G

[nitinvjain]

Issue Description

[Describe the issue in detail] I have been using srsRAN_4G with BladeRF 2.0 micro xa4. I was able to get ~70 Mbps in SISO TM1 mode for 100 PRB's. I am using a COTS 4G phone and it does support 2x2 mimo. I configured tm = 4 and nof_ports =2 to try out TM4 2x2 MIMO setup. There seems to be some issue as I can never get any speed more than 70 Mbps even though I have intel I9 machine.

I started checking configurations and how tm mode and nof_tb is at various points in the code and I can see that number of TB's is always 1.

As per release notes, TM3/TM4 should work.

Any quick inputs??

Setup Details

[Specify details of the test setup. This would help us reproduce the problem reliably] e.g. Network configuration, Operation System, Hardware, RF front-end, library and driver versions Ubuntu 22.04 LTS, Intel i9 13th gen core, bladeRF 2.0 micro xa4

Expected Behavior

[What you expect to happen] I should have seen almost doublt the DL throughput say close to ~140 Mbps.

Actual Behaviour

[What happens instead e.g. error message] I see only ~70 Mbps

Steps to reproduce the problem

[Tell us how to reproduce this issue e.g. RF setup, application config files] By configuring tm=4 and nof_ports = 2

Additional Information

[Any additional information, configuration or data that might be necessary to reproduce the issue]