Bluetooth: hci_sync: Fix accept list UAF during suspend

In the Linux kernel, the following vulnerability has been resolved:

Bluetooth: hci_sync: Fix accept list UAF during suspend

hci_update_event_filter_sync() walks hdev->accept_list while sending a
synchronous HCI command for each remote-wakeup device. The suspend path
holds hdev->req_lock, but accept-list updates are serialized by hdev->lock.
Consequently, remove_device() can free the current list entry during the
controller wait.

The following interleaving causes the use-after-free:

hci_update_event_filter_sync() remove_device()
fetch accept-list entry
hci_set_event_filter_sync()
wait for controller response hci_dev_lock()
list_del()
kfree()
hci_dev_unlock()
read the freed list.next

KASAN reported:

BUG: KASAN: slab-use-after-free in hci_suspend_sync+0x835/0x910
Read of size 8 at addr ffff88810bec8440 by task kworker/0:1/10
Workqueue: events vhci_suspend_work
Call Trace:
hci_suspend_sync+0x835/0x910
hci_suspend_dev+0x182/0x450
process_one_work+0x661/0x1090
worker_thread+0x45b/0xd10

Allocated by task 86:
hci_bdaddr_list_add_with_flags+0x1a8/0x400
add_device+0x381/0x820
hci_sock_sendmsg+0x1033/0x1ea0

Freed by task 91:
kfree+0x131/0x3c0
remove_device+0x429/0xb70
hci_sock_sendmsg+0x1033/0x1ea0

Snapshot the remote-wakeup addresses under hdev->lock. Release the lock
before sending HCI commands. Clear the controller event filter before
building the snapshot, and skip allocation and the second list traversal
when there are no matching entries. This preserves the original filter
and scan-state updates without retaining an accept-list node across a
controller wait.