Merge branch 'feature-21-TM7' of https://bitbucket.org/rdoost/openairinterface5g into feature-21-TM7

Updated conf to have 1 antenna for now.  Updated lte-softmodem.c to always take tx_sample_advance from the command line arguments.

Allow tx_sample_advance to be set from command line (UE) or conf file (eNB), and not be overriden in driver.

Some minor changes to iris_lib.cpp, added command line switch for setting UE remote address (Iris serial)

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