added longer prefix in PRACH symbol zero period for 15/30 kHz SCS. Both gNB and UE processing is modified. prachsim is functional again with new FAPI interfaces.

Merge branch 'NR_RRC_PRACH_procedures' of https://gitlab.eurecom.fr/oai/openairinterface5g into NR_RRC_PRACH_procedures

Merge branch 'NR_RRC_PRACH_procedures' of https://gitlab.eurecom.fr/oai/openairinterface5g into NR_RRC_PRACH_procedures

added handling for N_TA_OFFSET computation and changed some use of FAPI configuration in RU (used ru->config instead of ru->gNB_list[0]->config)

added scheduling of PRACH RX procedures in gNB and RU entities. Initialization of prach sequences added to nr_init.c

Merge branch 'NR_RRC_PRACH_procedures' of https://gitlab.eurecom.fr/oai/openairinterface5g into NR_RRC_PRACH_procedures

Conflicts:
	openair1/PHY/NR_TRANSPORT/nr_transport_proto.h
	openair2/LAYER2/NR_MAC_gNB/gNB_scheduler_RA.c

added FAPI interfaces int gNB prach receiver functions (rx_nr_prach,rx_nr_prach_ru) and in indication to MAC.

Merge branch 'NR_RRC_PRACH_procedures' of https://gitlab.eurecom.fr/oai/openairinterface5g into NR_RRC_PRACH_procedures

- using LTE function mac_rrc_nr_data_req_ue in noS1 mode
- cleanup code, comments
- fixes RA procedure
- Processing UL MAC PDU according to TS 38.321 ch 6.1:
- introduced function for gNB side UL PDU processing
- fixed bug in nr_ue_process_mac_pdu

- RA resource selection and transmission
- MAC header structs for RA
- RA procedure msg1 fixes
- code cleanup