submit_to_sms(): fix the use of deprecated gsm_septets2octets()

Change-Id: I9985972f0b1d2b71bfd133c5004201a3a0ffcbd0
diff --git a/TODO-RELEASE b/TODO-RELEASE
index 9c358ae..036a9b9 100644
--- a/TODO-RELEASE
+++ b/TODO-RELEASE
@@ -11,3 +11,4 @@
 osmo-msc	Mobile Identity Coding	OsmoMSC is stricter in rejecting invalid coding of Mobile Identity IEs
 libmosmo-mgcp-client		needs osmo-mgw.git > 1.7.0 (8667d5169df8d06e10ee3f3104e4cd533d15ac57), ABI break due to struct size in mgcp_conn_peer and mgcp_response
 osmo-msc			update version dependency to version with osmo_fd_*_{disable,enable}
+osmo-msc	smpp		migrate to gsm_septet_pack(), available since Ib1aac538afeb0a5c76a1df472d555139a496e12e
diff --git a/src/libmsc/smpp_openbsc.c b/src/libmsc/smpp_openbsc.c
index a79b252..54cd75b 100644
--- a/src/libmsc/smpp_openbsc.c
+++ b/src/libmsc/smpp_openbsc.c
@@ -250,8 +250,7 @@
 			sms_msg_len -= ud_len;
 			padbits = 7 - (ud_len % 7);
 		}
-		gsm_septets2octets(sms->user_data+ud_len, sms_msg,
-				   sms_msg_len, padbits);
+		gsm_septet_pack(sms->user_data+ud_len, sms_msg, sms_msg_len, padbits);
 		sms->user_data_len = (ud_len*8 + padbits)/7 + sms_msg_len;/* SEPTETS */
 		/* FIXME: sms->text */
 	} else {