Fix memory leaks in NAS generatePduSessionEstablishRequest

>Direct leak of 7 byte(s) in 1 object(s) allocated from:
    >0 0x7ffff74b4887 in __interceptor_malloc ../../../../src/libsanitizer/asan/asan_malloc_linux.cpp:145
    >1 0x55555819ab3c in generatePduSessionEstablishRequest /home/guido/repo/openairinterface5g/fix-ue-memory-leaks/openair3/NAS/NR_UE/nr_nas_msg_sim.c:938
    >2 0x5555581a8a9f in nas_nrue /home/guido/repo/openairinterface5g/fix-ue-memory-leaks/openair3/NAS/NR_UE/nr_nas_msg_sim.c:1295
    >3 0x5555581a3078 in nas_nrue_task /home/guido/repo/openairinterface5g/fix-ue-memory-leaks/openair3/NAS/NR_UE/nr_nas_msg_sim.c:1215
    >4 0x7ffff5e94ac2 in start_thread nptl/pthread_create.c:442

> Direct leak of 4 byte(s) in 1 object(s) allocated from:
    >0 0x7ffff74b4a57 in __interceptor_calloc ../../../../src/libsanitizer/asan/asan_malloc_linux.cpp:154
    >1 0x55555819c025 in generatePduSessionEstablishRequest /home/guido/repo/openairinterface5g/fix-ue-memory-leaks/openair3/NAS/NR_UE/nr_nas_msg_sim.c:993
    >2 0x5555581a8a9f in nas_nrue /home/guido/repo/openairinterface5g/fix-ue-memory-leaks/openair3/NAS/NR_UE/nr_nas_msg_sim.c:1295
    >3 0x5555581a3078 in nas_nrue_task /home/guido/repo/openairinterface5g/fix-ue-memory-leaks/openair3/NAS/NR_UE/nr_nas_msg_sim.c:1215
    >4 0x7ffff5e94ac2 in start_thread nptl/pthread_create.c:442

> Direct leak of 1 byte(s) in 1 object(s) allocated from:
    >0 0x7ffff74b4a57 in __interceptor_calloc ../../../../src/libsanitizer/asan/asan_malloc_linux.cpp:154
    >1 0x55555819c8f7 in generatePduSessionEstablishRequest /home/guido/repo/openairinterface5g/fix-ue-memory-leaks/openair3/NAS/NR_UE/nr_nas_msg_sim.c:987
    >2 0x5555581a9b75 in nas_nrue /home/guido/repo/openairinterface5g/fix-ue-memory-leaks/openair3/NAS/NR_UE/nr_nas_msg_sim.c:1299
    >3 0x5555581a414e in nas_nrue_task /home/guido/repo/openairinterface5g/fix-ue-memory-leaks/openair3/NAS/NR_UE/nr_nas_msg_sim.c:1219
    >4 0x7ffff5e94ac2 in start_thread nptl/pthread_create.c:442

openair3/NAS/NR_UE/nr_nas_msg_sim.c

@@ -1004,6 +1004,11 @@ static void generatePduSessionEstablishRequest(nr_ue_nas_t *nas, as_nas_info_t *
       security_header_len
       + mm_msg_encode(mm_msg, (uint8_t *)(initialNasMsg->data + security_header_len), size - security_header_len);
 
+  // Free allocated memory after encode
+  free(req_buffer);
+  free(mm_msg->uplink_nas_transport.dnn.value);
+  free(mm_msg->uplink_nas_transport.snssai.value);
+
   /* ciphering */
   uint8_t buf[initialNasMsg->length - 7];
   stream_cipher.context = nas->security_container->ciphering_context;