Bluetooth: hci_sync: use hci_skb_event() helper

This instance is the only opencoded version of the macro, so have it
follow suit.
Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

net/bluetooth/hci_request.c

@@ -261,7 +261,7 @@ void hci_req_add_ev(struct hci_request *req, u16 opcode, u32 plen,
 	if (skb_queue_empty(&req->cmd_q))
 		bt_cb(skb)->hci.req_flags |= HCI_REQ_START;
 
-	bt_cb(skb)->hci.req_event = event;
+	hci_skb_event(skb) = event;
 
 	skb_queue_tail(&req->cmd_q, skb);
 }