Bluetooth: hci_sock: purge socket queues in the destruct() callback

The receive path may take the socket right before hci_sock_release(),
but it may enqueue the packets to the socket queues after the call to
skb_queue_purge(), therefore the socket can be destroyed without clear
its queues completely.

Moving these skb_queue_purge() to the hci_sock_destruct() will fix this
issue, because nothing is referencing the socket at this point.

Signed-off-by: Nguyen Dinh Phi <phind.uet@gmail.com>
Reported-by:  <syzbot+4c4ffd1e1094dae61035@syzkaller.appspotmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>