Bluetooth: Delete unused hci_req_prepare_suspend() declaration

hci_req_prepare_suspend() has been deprecated in favor of
hci_suspend_sync().

Fixes: 182ee45d ("Bluetooth: hci_sync: Rework hci_suspend_notifier")
Signed-off-by: Yao Xiao <xiaoyao@rock-chips.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

net/bluetooth/hci_request.h

@@ -71,7 +71,5 @@ struct sk_buff *hci_prepare_cmd(struct hci_dev *hdev, u16 opcode, u32 plen,
 void hci_req_add_le_scan_disable(struct hci_request *req, bool rpa_le_conn);
 void hci_req_add_le_passive_scan(struct hci_request *req);
 
-void hci_req_prepare_suspend(struct hci_dev *hdev, enum suspended_state next);
-
 void hci_request_setup(struct hci_dev *hdev);
 void hci_request_cancel_all(struct hci_dev *hdev);