Bluetooth: implement read/set default system parameters mgmt

This patch implements the read default system parameters and the set
default system parameters mgmt commands.

Signed-off-by: Alain Michaud <alainm@chromium.org>
Reviewed-by: Abhishek Pandit-Subedi <abhishekpandit@chromium.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

net/bluetooth/mgmt_config.h

@@ -0,0 +1,11 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+/*
+ * Copyright (C) 2020 Google Corporation
+ */
+
+int read_def_system_config(struct sock *sk, struct hci_dev *hdev, void *data,
+			   u16 data_len);
+
+int set_def_system_config(struct sock *sk, struct hci_dev *hdev, void *data,
+			  u16 data_len);