Bluetooth: Add support for external configuration with UART driver

The quirk for enabling external configuration with UART needs to be
provided via the HCI UART flags. Add a new flag for it and declare
it as valid.

Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
diff --git a/drivers/bluetooth/hci_uart.h b/drivers/bluetooth/hci_uart.h
index 12df101..247488e 100644
--- a/drivers/bluetooth/hci_uart.h
+++ b/drivers/bluetooth/hci_uart.h
@@ -48,6 +48,7 @@
 #define HCI_UART_RESET_ON_INIT	1
 #define HCI_UART_CREATE_AMP	2
 #define HCI_UART_INIT_PENDING	3
+#define HCI_UART_EXT_CONFIG	4
 
 struct hci_uart;