Improve Precoding Matrix computation taking in consideration the DCI format

This main goal of this Merge Request is to fix this assertion that happens during a RRCReestablishment procedure:

Assertion (1==0) failed!
In get_pm_index() /home/user/openairinterface5g/openair2/LAYER2/NR_MAC_gNB/gNB_scheduler_primitives.c:163
More than 2 antenna ports not yet supported

More details to be added later...