Bluetooth: hci_uart: Fix dereferencing of ERR_PTR

If h4_recv_buf() return ERR_PTR instead sk_buff pointer, it should be
cleared once PTR_ERR is completed for the further dereference such as
h4_recv(), or h4_close().

Signed-off-by: Chan-yeol Park <chanyeol.park@samsung.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

drivers/bluetooth/hci_ath.c

@@ -192,6 +192,7 @@ static int ath_recv(struct hci_uart *hu, const void *data, int count)
 	if (IS_ERR(ath->rx_skb)) {
 		int err = PTR_ERR(ath->rx_skb);
 		BT_ERR("%s: Frame reassembly failed (%d)", hu->hdev->name, err);
+		ath->rx_skb = NULL;
 		return err;
 	}