Bluetooth: Add configuration support for ERTM and Streaming mode

Add support to config_req and config_rsp to configure ERTM and Streaming
mode. If the remote device specifies ERTM or Streaming mode, then the
same mode is proposed. Otherwise ERTM or Basic mode is used. And in case
of a state 2 device, the remote device should propose the same mode. If
not, then the channel gets disconnected.

Signed-off-by: Gustavo F. Padovan <gustavo@las.ic.unicamp.br>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
static int l2cap_disconn_ind(struct hci_conn *hcon)
{
	struct l2cap_conn *conn = hcon->l2cap_data;

	BT_DBG("hcon %p", hcon);

	if (hcon->type != ACL_LINK || !conn)
		return 0x13;

	return conn->disc_reason;
}

static int l2cap_disconn_ind(struct hci_conn *hcon)
{
	struct l2cap_conn *conn = hcon->l2cap_data;

	BT_DBG("hcon %p", hcon);

	if (hcon->type != ACL_LINK || !conn)
		return 0x13;

	return conn->disc_reason;
}
