nm_statechg_signal_data: Convert state ptr to data

There's no need to use pointers there, it is only asking for errors from
code handling the data structe from the signal by attempting to change
them. Even for mem size point of view it doesn't make sense, since it's
3 byte vs a 4 byte pointer.

Furthermore, this is a preparation for new commit, where the NM object
current state will be updated before emitting the signal. This patch
eases a lot the follow up mentioned patch.

Change-Id: I9b648dfd8392b7b40bfe2b38f3345017481f5129
---
M include/osmocom/bsc/signal.h
M src/ipaccess/ipaccess-config.c
M src/osmo-bsc/abis_nm.c
M src/osmo-bsc/abis_om2000.c
M src/osmo-bsc/acc.c
M src/osmo-bsc/nm_bb_transc_fsm.c
M src/osmo-bsc/nm_bts_fsm.c
M src/osmo-bsc/nm_bts_sm_fsm.c
M src/osmo-bsc/nm_channel_fsm.c
M src/osmo-bsc/nm_gprs_cell_fsm.c
M src/osmo-bsc/nm_gprs_nse_fsm.c
M src/osmo-bsc/nm_gprs_nsvc_fsm.c
M src/osmo-bsc/nm_rcarrier_fsm.c
13 files changed, 98 insertions(+), 102 deletions(-)