When the program exits it has to stop the streaming of the USRP.
The function exit_fun is supposed to do that. When quitting with
control+c (very common case) this function is not called. The
code is very unclear there, so let's add a stop_rf in the RU,
as there is already a start_rf.

If we don't call trx_end_func, then at the next run the USRP
device may be in an unstable state and behave improperly.

If the program crashes then the USRP device may be in an
unstable state. The only solution to this problem is to reset
the USRP device.

Maybe there is a way to clean the state of the device when we
open it, before we start using it. Sort of a cleanup before
use. That could be a better solution to "bad state after program
crash".

What has been tested:
- monolithic eNB only

I tried to change rx and tx attenuation by the config file, but they are not changed. The bug is because att_rx and att_tx do not put in RC.rru when local_rf is "yes" in config file. We need to put att_rx and att_rx for both local_rf = "yes" and "no". Also RF config which send to RF device must be fill by this parameters.

- add function free_td() -> complements init_td() [seems to not be used, added
  for completeness]
- add function free_td8() -> undoes init_td8() [free memory of 8-bit LLR Turbo
  decoder]
- add function free_td16() -> undoes init_td16() [free memory of 16-bit LLR
  Turbo decoder]
- change function free_tdavx216() -> undoes init_tdavx216() [free memory of
  16-bit LLR Turbo decoder, AVX2 version]
- add free_lte_top() -> frees memory allocated by init_lte_top()
- change free_ul_ref_sigs() to set freed pointers to NULL
- add method free_transport() -> frees memory of ULSCH/DLSCH transport channels
- use the above functions when stopping/restarting the lte-softmodem

this methods free the memory that is allocated by the functions
phy_init_RU() and phy_init_lte_eNB()

- add set_function_spec_param() which configures RU_t instance depending on its
  function(al split)
- export more functions like kill_RU_proc() so that they can be reused by
  restart functionality

fixes after merge with develop. Partial UE/eNB separation in build to avoid problems with NFAPI in oaisim UE/RRU.
tested with simulator.

This commit fixes issues introduced by the previous commit.

Summary of work:
- cleanup:
  - fix LOG_XX to be less verbose
  - fix cmake_targets/CMakeLists.txt
  - fix oaienv
  - remove dead code
- bug fixes:
  - in openair1/SCHED/fapi_l1.c we had:
      eNB->pdcch_vars[subframe&1].num_dci           = number_dci;
    should be:
      eNB->pdcch_vars[subframe&1].num_dci           = 0;
    This bug let the PHY send more DCIs than what should have been
    sent because num_dci is incremented later on in the code.
    This fix may be a problem for fapi mode, to be checked.
  - add new T VCD traces
  - revert openair1/PHY/TOOLS/file_output.c to 'develop' version
  - remove thread_id in logRecord/logRecord_mt
  - revert (and adapt) configuration files
  - be careful when doing frame++, we need to % 1024
  - revert target_rx_power in openair2/LAYER2/MAC/eNB_scheduler_ulsch.c
- NFAPI:
  - the open-nFAPI code has been included in the repository. See nfapi/README.
    Maybe we should "git clone" the Cisco repository instead. We have to be
    careful of availability though.

What has been tested:
- monolithic eNB FDD 5/10MHz with one UE, iperf UDP/TCP uplink/downlink

Anything else may fail to work, especially the FAPI mode, which has not
been tested at all.

It has been chosen to not include the full history of commits
from David. He included a binary version of wireshark, probably
a modified one that understands NFAPI. Wireshark is released under
the GPL license, we cannot include it in the repository. We could
have done a next commit to remove this binary. But then it would
still be present in the history of commits, which may not be allowed.
And it would take space on disk. We could edit the history to remove
wireshark entirely. But this operation is too complicated.

There was also a pcap capture file, which has nothing to do in
the history of commits and would take space on disk. There again,
it's too difficult to edit the history to remove it.

There was a file .gitignore that was also removed.

The original history can be found on David's repository:
https://gitlab.eurecom.fr/daveprice/openairinterface5g/
The branch is: nfapi-ru-rau-split.

A copy of that branch has been included in the internal OAI
repository, for those who have access to it.
The branch is the same. The last commit ID is
9106438239e0bc626ff1fa1d97d911caadd0fbb9.

You can compare the current commit with the commit 9106...
to see what differs.

The current commit has to be considered non-working.
The commit following the current commit will fix problems with
the work in the current commit.

If you use git bisect, don't spend time analyzing the current
commit.