[Bluetooth] Always include MTU in L2CAP config responses

When sending a positive config response it shall include the actual
MTU to be used on this channel. This differs from the Bluetooth 1.1
specification where it was enough to acknowledge the config request.
Signed-off-by: NMarcel Holtmann <marcel@holtmann.org>

net/bluetooth/l2cap.c

@@ -1353,12 +1353,12 @@ static inline int l2cap_conf_output(struct sock *sk, void **ptr)
 
 	/* Configure output options and let the other side know
 	 * which ones we don't like. */
-	if (pi->conf_mtu < pi->omtu) {
-		l2cap_add_conf_opt(ptr, L2CAP_CONF_MTU, 2, pi->omtu);
+	if (pi->conf_mtu < pi->omtu)
 		result = L2CAP_CONF_UNACCEPT;
-	} else {
+	else
 		pi->omtu = pi->conf_mtu;
-	}
+
+	l2cap_add_conf_opt(ptr, L2CAP_CONF_MTU, 2, pi->omtu);
 
 	BT_DBG("sk %p result %d", sk, result);
 	return result;