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/bts_ipaccess_nanobts.c b/openbsc/src/libbsc/bts_ipaccess_nanobts.c
index 25dc0c8..463e3a7 100644
--- a/openbsc/src/libbsc/bts_ipaccess_nanobts.c
+++ b/openbsc/src/libbsc/bts_ipaccess_nanobts.c
@@ -258,6 +258,9 @@
 	struct gsm_bts_trx_ts *ts;
 	struct gsm_bts_gprs_nsvc *nsvc;
 
+	if (nsd->bts->type != GSM_BTS_TYPE_NANOBTS)
+		return 0;
+
 	/* This event-driven BTS setup is currently only required on nanoBTS */
 
 	/* S_NM_STATECHG_ADM is called after we call chg_adm_state() and would create