Merge branch 'feature-21-TM7' of https://gitlab.eurecom.fr/oai/openairinterface5g into feature-21-TM7

Merge branch 'feature-21-TM7' of https://gitlab.eurecom.fr/oai/openairinterface5g into feature-21-TM7

Merge branch 'feature-21-TM7' of https://gitlab.eurecom.fr/oai/openairinterface5g into feature-21-TM7

reduced the max number of antenna ports to 6 to save memory (we are not using antenna port >5 anyway)
mult_cpx_conj_vector can now also do multiply add
beam_precoding now uses mult_cpx_conj_vector

Conflicts:
	targets/RT/USER/lte-enb.c

Develop integration w50

See merge request !61

We have a crash:

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7fff7387d700 (LWP 1944)]
ulsch_decoding (eNB=eNB@entry=0x7fffaf73b010, proc=proc@entry=0x7fffaf73b480,
    UE_id=UE_id@entry=0 '\000',
    control_only_flag=control_only_flag@entry=0 '\000',
    Nbundled=<optimised out>, llr8_flag=<optimised out>)
    at /roux/merge/openairinterface5g/openair1/PHY/LTE_TRANSPORT/ulsch_decoding.c:1450
1450          *((__m256i *)&ulsch_harq->e[iprime]) = *((__m256i *)&y[j2]);

This commit reduces the apparition of the crash, but does not
eliminate it completely.

To be fixed after integration.