bsc_api: Change submit dtap to allow to automatically use the SACH

For SAPI=3 on a TCH it might be nice to use the SACH to submit
the message. The api allows to automatically use the SACH if
a message like this is submitted.
diff --git a/openbsc/src/gsm_04_11.c b/openbsc/src/gsm_04_11.c
index 2931026..c46f772 100644
--- a/openbsc/src/gsm_04_11.c
+++ b/openbsc/src/gsm_04_11.c
@@ -142,7 +142,7 @@
 {
 	DEBUGP(DSMS, "GSM4.11 TX %s\n", hexdump(msg->data, msg->len));
 	msg->l3h = msg->data;
-	return gsm0808_submit_dtap(conn, msg, link_id);
+	return gsm0808_submit_dtap(conn, msg, link_id, 1);
 }
 
 /* SMC TC1* is expired */