db: Fix compile warning, declare db_sms_get_unsent_by_subscr

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
diff --git a/openbsc/include/openbsc/db.h b/openbsc/include/openbsc/db.h
index fca7364..8059668 100644
--- a/openbsc/include/openbsc/db.h
+++ b/openbsc/include/openbsc/db.h
@@ -46,6 +46,7 @@
 /* SMS store-and-forward */
 int db_sms_store(struct gsm_sms *sms);
 struct gsm_sms *db_sms_get_unsent(struct gsm_network *net, int min_id);
+struct gsm_sms *db_sms_get_unsent_by_subscr(struct gsm_network *net, int min_subscr_id);
 struct gsm_sms *db_sms_get_unsent_for_subscr(struct gsm_subscriber *subscr);
 int db_sms_mark_sent(struct gsm_sms *sms);