Bluetooth: btusb: fix non-atomic allocation in completion handler

USB completion handlers are called in atomic context and must
specifically not allocate memory using GFP_KERNEL.

Fixes: a1c49c43 ("Bluetooth: btusb: Add protocol support for MediaTek MT7668U USB devices")
Cc: stable <stable@vger.kernel.org>     # 5.3
Cc: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

drivers/bluetooth/btusb.c

@@ -2602,7 +2602,7 @@ static void btusb_mtk_wmt_recv(struct urb *urb)
 		 * and being processed the events from there then.
 		 */
 		if (test_bit(BTUSB_TX_WAIT_VND_EVT, &data->flags)) {
-			data->evt_skb = skb_clone(skb, GFP_KERNEL);
+			data->evt_skb = skb_clone(skb, GFP_ATOMIC);
 			if (!data->evt_skb)
 				goto err_out;
 		}