abis_nm: fix some fallout regarding abis_nm migration to libosmocore

Thanks to Holger for noticing this.
diff --git a/openbsc/src/libbsc/bsc_vty.c b/openbsc/src/libbsc/bsc_vty.c
index 12f9ffd..f1e964c 100644
--- a/openbsc/src/libbsc/bsc_vty.c
+++ b/openbsc/src/libbsc/bsc_vty.c
@@ -132,8 +132,8 @@
 static void net_dump_nmstate(struct vty *vty, struct gsm_nm_state *nms)
 {
 	vty_out(vty,"Oper '%s', Admin %u, Avail '%s'%s",
-		nm_opstate_name(nms->operational), nms->administrative,
-		nm_avail_name(nms->availability), VTY_NEWLINE);
+		abis_nm_opstate_name(nms->operational), nms->administrative,
+		abis_nm_avail_name(nms->availability), VTY_NEWLINE);
 }
 
 static void dump_pchan_load_vty(struct vty *vty, char *prefix,