OML: Include a pointer to the BTS in NM STATE CHANGE signals

... this allows the BTS driver to decide if it should handle the event at all
diff --git a/openbsc/src/libbsc/abis_nm.c b/openbsc/src/libbsc/abis_nm.c
index 788dd4d..761dda1 100644
--- a/openbsc/src/libbsc/abis_nm.c
+++ b/openbsc/src/libbsc/abis_nm.c
@@ -697,6 +697,7 @@
 	new_state = *nm_state;
 	new_state.administrative = adm_state;
 
+	nsd.bts = bts;
 	nsd.obj_class = obj_class;
 	nsd.old_state = nm_state;
 	nsd.new_state = &new_state;
@@ -759,6 +760,7 @@
 		nsd.old_state = nm_state;
 		nsd.new_state = &new_state;
 		nsd.obj_inst = &foh->obj_inst;
+		nsd.bts = bts;
 		dispatch_signal(SS_NM, S_NM_STATECHG_OPER, &nsd);
 		nm_state->operational = new_state.operational;
 		nm_state->availability = new_state.availability;