Introduce slot indication tick to run (DL) scheduler

The next commit introduces a separate gNB TX processing thread. To
properly separate DL scheduler (for scheduling decisions) from UL
indication handling (for UL packets), this commit introduces a slot
indication "tick" to run the DL scheduler which will be put into the gNB
TX processing chain instead of the UL indication.

openair2/NR_PHY_INTERFACE/NR_IF_Module.h

@@ -113,6 +113,7 @@ typedef struct NR_IF_Module_s {
   //define the function pointer
   void (*NR_UL_indication)(NR_UL_IND_t *UL_INFO);
   void (*NR_Schedule_response)(NR_Sched_Rsp_t *Sched_INFO);
+  void (*NR_slot_indication)(module_id_t module_idP, int CC_id, int frame, int slot);
   void (*NR_PHY_config_req)(NR_PHY_Config_t *config_INFO);
   uint32_t CC_mask;
   uint16_t current_frame;