fix compile issues, simplify gtp send function

openair1/SIMULATION/NR_PHY/dlschsim.c

openair1/SIMULATION/NR_PHY/dlsim.c

openair1/SIMULATION/NR_PHY/nr_dummy_functions.c

openair1/SIMULATION/NR_PHY/nr_unitary_defs.h

openair1/SIMULATION/NR_PHY/pbchsim.c

openair1/SIMULATION/NR_PHY/prachsim.c

openair1/SIMULATION/NR_PHY/pucchsim.c

openair1/SIMULATION/NR_PHY/ulschsim.c

openair1/SIMULATION/NR_PHY/ulsim.c

openair2/COMMON/e1ap_messages_types.h

openair2/E1AP/e1ap_common.h

openair3/ocp-gtpu/gtp_itf.h