solve warnings (related to NAS) when compiling SMF

src/nas/3gpp_24.501.h

src/nas/ies/MessageType.c

src/nas/ies/MessageType.h

src/nas/ies/NSSAI.c

src/nas/ies/QOSRules.c

src/nas/ies/SecurityHeaderType.c

src/nas/ies/TimeZone.c

src/nas/ies/_5GSMCapability.c

src/nas/ies/_5GSMobileIdentity.c

src/nas/mm/msg/DeregistrationRequest.c

src/nas/mm/msg/RegistrationRequest.c

src/nas/mm/msg/ServiceRequest.c

src/nas/mm/msg/mm_msg.c

src/nas/nas_message.c

src/nas/sm/msg/PDUSessionModificationCommand.c

src/nas/sm/sm_msg.c