gsm0808: Fix the format of the clear IE...

This is really TLV...
diff --git a/src/gsm0808.c b/src/gsm0808.c
index 2424d8c..3962baa 100644
--- a/src/gsm0808.c
+++ b/src/gsm0808.c
@@ -115,8 +115,9 @@
 	if (!msg)
 		return NULL;
 
-	msg->l3h = msgb_tv_put(msg, BSSAP_MSG_BSS_MANAGEMENT, 2);
-	msgb_tv_put(msg, BSS_MAP_MSG_CLEAR_CMD, reason);
+	msg->l3h = msgb_tv_put(msg, BSSAP_MSG_BSS_MANAGEMENT, 4);
+	msgb_v_put(msg, BSS_MAP_MSG_CLEAR_CMD);
+	msgb_tlv_put(msg, GSM0808_IE_CAUSE, 1, &reason);
 	return msg;
 }