PRACH_PDU.prach_format now interpreted according to last version (March 2020) of 5G FAPI specs
fixing nr_prachsim

- Fixed random preamble selection in contention-based RA
- Cleaned-up comments and commented code

use snprintf() instead of sprintf() to avoid writes outside buffer limits

  - Added support for FR1 in RO selection
  -RACH preamble selected according to the chosen RO

- replacing ambiguous configuration of N_RB for extraction of DCI 1_0

- added some text descriptions
- replaced active BWP with initial BWP in Msg3 scheduling (8.3 TS 38.213)
- fixed logging
- disabled Msg3 repetitions after first transmission (disabled RA @ MAC)

- moved remaining PUSCH PDU configuration from ULSCH
  procedures entirely to MAC
- introduced a function for DMRS RE configuration
- cleaned up redundant code in ULSCH procedures
- fixed TBS computation for Msg3

- redundant code for the configuration of the scheduled_response was removed
- scheduled response is not needed to be stored in the NR_UE_MAC_INST struct as it passed to the function right away

- calling nr_ue_scheduled_response after pdu preparation
- increasing the number_pdus before response scheduling
- resetting after dl/ul config pdu handling

- extraction of resource allocation from Msg2
- configuration of Msg3 PDU
- Msg3 scheduling
- MAC/PHY interface adaptations

Check the provided MCS index according to the specified table.
Some tables go up to MCS index 27, others up to MCS index 28.
If the MCS index exceeds the allowed limit, assume max. MCS.

removed AssertFatal in nr_ue_mac_procedures.c for nr_dlsim HARQ tests. For some unknown reason there are occasion 0 SDUs sent up to MAC which causes failure.

Set n_dmrs_cdm_groups = 1 for now.
Should be fixed accordingly to TS 38.214 section 5.1.6.2
using tables 7.3.1.2.2-1, 7.3.1.2.2-2, 7.3.1.2.2-3, 7.3.1.2.2-4 of TS 38.212

- DM-RS type {1,2} was wrongly assigned to {1,2} instead of {0,1}
- Num DM-RS CDM groups without data is now taken into account in mthread
  decoding function
- number of DM-RS CDM groups without data for format 1_0 according to 5.1.6.2
  3GPP TS 38.214 version 15.9.0 Release 15:
-- the UE shall assume the number of DM-RS CDM groups without data is:
-- 1 (CDM group 0) for the case of PDSCH with allocation duration of 2 symb
-- 2 (CDM group {0,1}) for all other cases.