This reverts commit a986e709.

We cannot really enable slots in both TDD periods, because the way we
receive HARQ feedback is not ready and OAI-UE does not seem to support
it.

Note: the slots to "enable" depend on the TDD configuration, so instead
of configuring it statically, we should read it from the configuration
file.

- No dynamic allocation of PUCCH structures
- Use first PUCCH for HARQ (can only allocate for up to two slots in
  single PUCCH, simplistic nr_acknack_scheduling!)
- Use second PUCCH for CSI, do not multiplex!

MR969: Develop oriecpriupdates  
Makes IF5 functionality compatible with ECPRI user-plane. 
Control-plane functionality for supporting third-party RRUs : provides an interface converting OAI-native RF parameters, a subset of LTE framing parameters, and RF streaming activation/deactivation to a wrapper (libthirdparty_transpro.so) which uses the proprietary interface of the RRU. 
This branch was tested with a commercial eCPRI RRU from AW2S.

MR980: Nr ul scheduler basis 
- cleanup of UL scheduler, and add interface preprocessor-postprocessor (in `NR_UE_sched_ctrl_t`)
- Postprocessor can (almost) handle multiple UEs. Preprocessor will follow soon (proportional fair scheduler)
- Preprocessor for phytest (always schedule 50 RBs due to OAI UE limitations) and real UE (as many resources as possible)
- Internal structures have been updated: the `UL_tti_req` structure became an array (as `UL_tti_req_ahead`) so that we can schedule in advance and mark resources as used. Before, we would keep the corresponding nfapi message structure per UE, which could get messy when we have many UEs.

There are no functional changes (UL/DL performance is the same). 

MR987: Nr phy mac if multi ue  
- Handles multiple UEs in `NR_IF_interface.c`
- Some minor clean up

MR979: Pusch decoder threads parameter  
- Added a config file parameter for specifying the number of threads to be used for PUSCH decoding.

MR982: nr pdcp: use pdcp config
-There was a problem with SN size. It was hardcoded to 12 bits (so max sn = 4095) but we configure the UE with 18 bits. 
Get the correct value from pdcp_Config.
- Store also discard_timer and t_reordering that will be used later by a proper NR PDCP layer 

MR984: NR FR2 SSB
- several fixes mainly concerning FR2 synchronization and RA both at gNB and UE
- SSB RRC signaling for FR2
- Coreset RRC for FR2
- SSB detection in FR2 for SSB index > 15
- Adjust sync function issue
- Fix for scheduling of MSG2 (issue with sl_ahead)

Conflicts:
	openair2/LAYER2/NR_MAC_gNB/gNB_scheduler_RA.c