Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/drivers/bluetooth/hci_ath.c b/drivers/bluetooth/hci_ath.c
index d568fbd..dbfe346 100644
--- a/drivers/bluetooth/hci_ath.c
+++ b/drivers/bluetooth/hci_ath.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  *  Atheros Communication Bluetooth HCIATH3K UART protocol
  *
@@ -9,21 +10,6 @@
  *  Acknowledgements:
  *  This file is based on hci_h4.c, which was written
  *  by Maxim Krasnyansky and Marcel Holtmann.
- *
- *  This program is free software; you can redistribute it and/or modify
- *  it under the terms of the GNU General Public License as published by
- *  the Free Software Foundation; either version 2 of the License, or
- *  (at your option) any later version.
- *
- *  This program is distributed in the hope that it will be useful,
- *  but WITHOUT ANY WARRANTY; without even the implied warranty of
- *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *  GNU General Public License for more details.
- *
- *  You should have received a copy of the GNU General Public License
- *  along with this program; if not, write to the Free Software
- *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
- *
  */
 
 #include <linux/module.h>
@@ -112,6 +98,9 @@
 
 	BT_DBG("hu %p", hu);
 
+	if (!hci_uart_has_flow_control(hu))
+		return -EOPNOTSUPP;
+
 	ath = kzalloc(sizeof(*ath), GFP_KERNEL);
 	if (!ath)
 		return -ENOMEM;