UPSTREAM: Bluetooth: hci_sync: add lock to protect HCI_UNREGISTER

[ Upstream commit 1857c199 ]

When the HCI_UNREGISTER flag is set, no jobs should be scheduled. Fix
potential race when HCI_UNREGISTER is set after the flag is tested in
hci_cmd_sync_queue.

Fixes: 0b94f265 ("Bluetooth: hci_sync: Fix queuing commands when HCI_UNREGISTER is set")
Change-Id: I565a2ad87dc2ce4fd62ee0d09a5d28342fec8ad3
Signed-off-by: Zhengping Jiang <jiangzp@google.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
(cherry picked from commit 17aac120)
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>