Bluetooth: Add stubs for synchronous HCI request functionality

Prepare hci_request.c to have code for doing synchronous HCI requests,
such as LE scanning or advertising changes. The necessary work
callbacks will be set up in hci_request_setup() and cleaned up in
hci_request_cancel_all(). The former is used when an HCI device get
registered, and the latter each time it is powered off (or
unregistered).

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
index ec1beba..965bc01 100644
--- a/net/bluetooth/hci_core.c
+++ b/net/bluetooth/hci_core.c
@@ -1609,6 +1609,8 @@
 
 	hci_req_sync_unlock(hdev);
 
+	hci_request_cancel_all(hdev);
+
 	hci_dev_put(hdev);
 	return 0;
 }
@@ -3161,6 +3163,8 @@
 
 	INIT_DELAYED_WORK(&hdev->cmd_timer, hci_cmd_timeout);
 
+	hci_request_setup(hdev);
+
 	hci_init_sysfs(hdev);
 	discovery_init(hdev);