Further cleanup: define oai_exit for 4G

The parent commit cleans up and groups oai_exit in one place,
nr-softmodem-common.h. Therefore, this 5G file is included in the 4G
defs_common.h (at least it's mostly 4G), which is not nice. Instead,
define oai_exit also in 4G softmodem-common.h, and include this in
defs_common.h. Remove the cyclic inclusion of defs_common.h in
softmodem-common.h, and resolve all subsequent errors around unknown
types and extern definition mismatches.

openair1/SCHED/nfapi_lte_dummy.c

@@ -22,7 +22,7 @@ void handle_nfapi_nr_csirs_pdu(processingData_L1tx_t *msgTx,
                     }                           
 int l1_north_init_gNB(void){return 0;}
 
-uint8_t slot_ahead=6;
+int slot_ahead = 6;
 //uint8_t nfapi_mode=0;
 NR_IF_Module_t *NR_IF_Module_init(int Mod_id) {return NULL;}
 

openair1/SCHED/nfapi_nr_dummy.c

@@ -22,7 +22,7 @@ void handle_nfapi_nr_csirs_pdu(processingData_L1tx_t *msgTx,
                     }
 int l1_north_init_gNB(void){return 0;}
 
-uint8_t slot_ahead=6;
+int slot_ahead = 6;
 //uint8_t nfapi_mode=0;
 NR_IF_Module_t *NR_IF_Module_init(int Mod_id) {return NULL;}