ranap_msg_factory: Fix endianess in paging command

the asn1 helper functions already take care of byte ordering, so use these.
diff --git a/src/ranap_msg_factory.c b/src/ranap_msg_factory.c
index 041e546..401ef4e 100644
--- a/src/ranap_msg_factory.c
+++ b/src/ranap_msg_factory.c
@@ -417,16 +417,13 @@
 
 	if (tmsi) {
 		uint32_t *tmsi_buf = CALLOC(1, sizeof(*tmsi_buf));
-		*tmsi_buf = *tmsi;
 		ies.presenceMask |= PAGINGIES_RANAP_TEMPORARYUE_ID_PRESENT;
 		if (is_ps) {
 			ies.temporaryUE_ID.present = RANAP_TemporaryUE_ID_PR_p_TMSI;
-			ies.temporaryUE_ID.choice.tMSI.buf = (uint8_t *) tmsi_buf;
-			ies.temporaryUE_ID.choice.tMSI.size = sizeof(*tmsi_buf);
+			asn1_u32_to_str(&ies.temporaryUE_ID.choice.tMSI, tmsi_buf, *tmsi);
 		} else {
 			ies.temporaryUE_ID.present = RANAP_TemporaryUE_ID_PR_tMSI;
-			ies.temporaryUE_ID.choice.p_TMSI.buf = (uint8_t *) tmsi_buf;
-			ies.temporaryUE_ID.choice.p_TMSI.size = sizeof(*tmsi_buf);
+			asn1_u32_to_str(&ies.temporaryUE_ID.choice.p_TMSI, tmsi_buf, *tmsi);
 		}
 	}