HO: Changed availablilty of ts_is_usable() from static to extern

Change-Id: I3471e38327c4b98490faed9b604fb76438ba9954
diff --git a/include/osmocom/bsc/chan_alloc.h b/include/osmocom/bsc/chan_alloc.h
index 62d0286..f2a75c5 100644
--- a/include/osmocom/bsc/chan_alloc.h
+++ b/include/osmocom/bsc/chan_alloc.h
@@ -47,5 +47,6 @@
 void network_chan_load(struct pchan_load *pl, struct gsm_network *net);
 
 bool trx_is_usable(const struct gsm_bts_trx *trx);
+bool ts_is_usable(const struct gsm_bts_trx_ts *ts);
 
 #endif /* _CHAN_ALLOC_H */