The smp_unregister() function needs to be called every time the
controller is powered down. There are multiple entry points when
this can happen. One is "hciconfig hci0 reset" which will throw
a WARN_ON when LE support has been enabled.

[   78.564620] WARNING: CPU: 0 PID: 148 at net/bluetooth/smp.c:3075 smp_register+0xf1/0x170()
[   78.564622] Modules linked in:
[   78.564628] CPU: 0 PID: 148 Comm: kworker/u3:1 Not tainted 3.19.0-rc4-devel+ #404
[   78.564629] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
[   78.564635] Workqueue: hci0 hci_rx_work
[   78.564638]  ffffffff81b4a7a2 ffff88001cb2fb38 ffffffff8161d881 0000000080000000
[   78.564642]  0000000000000000 ffff88001cb2fb78 ffffffff8103b870 696e55206e6f6f6d
[   78.564645]  ffff88001d965000 0000000000000000 0000000000000000 ffff88001d965000
[   78.564648] Call Trace:
[   78.564655]  [<ffffffff8161d881>] dump_stack+0x4f/0x7b
[   78.564662]  [<ffffffff8103b870>] warn_slowpath_common+0x80/0xc0
[   78.564667]  [<ffffffff81544b00>] ? add_uuid+0x1f0/0x1f0
[   78.564671]  [<ffffffff8103b955>] warn_slowpath_null+0x15/0x20
[   78.564674]  [<ffffffff81562d81>] smp_register+0xf1/0x170
[   78.564680]  [<ffffffff81081236>] ? lock_timer_base.isra.30+0x26/0x50
[   78.564683]  [<ffffffff81544bf0>] powered_complete+0xf0/0x120
[   78.564688]  [<ffffffff8152e622>] hci_req_cmd_complete+0x82/0x260
[   78.564692]  [<ffffffff8153554f>] hci_cmd_complete_evt+0x6cf/0x2e20
[   78.564697]  [<ffffffff81623e43>] ? _raw_spin_unlock_irqrestore+0x13/0x30
[   78.564701]  [<ffffffff8106b0af>] ? __wake_up_sync_key+0x4f/0x60
[   78.564705]  [<ffffffff8153a2ab>] hci_event_packet+0xbcb/0x2e70
[   78.564709]  [<ffffffff814094d3>] ? skb_release_all+0x23/0x30
[   78.564711]  [<ffffffff81409529>] ? kfree_skb+0x29/0x40
[   78.564715]  [<ffffffff815296c8>] hci_rx_work+0x1c8/0x3f0
[   78.564719]  [<ffffffff8105bd91>] ? get_parent_ip+0x11/0x50
[   78.564722]  [<ffffffff8105be25>] ? preempt_count_add+0x55/0xb0
[   78.564727]  [<ffffffff8104f65f>] process_one_work+0x12f/0x360
[   78.564731]  [<ffffffff8104ff9b>] worker_thread+0x6b/0x4b0
[   78.564735]  [<ffffffff8104ff30>] ? cancel_delayed_work_sync+0x10/0x10
[   78.564738]  [<ffffffff810542fa>] kthread+0xea/0x100
[   78.564742]  [<ffffffff81620000>] ? __schedule+0x3e0/0x980
[   78.564745]  [<ffffffff81054210>] ? kthread_create_on_node+0x180/0x180
[   78.564749]  [<ffffffff816246ec>] ret_from_fork+0x7c/0xb0
[   78.564752]  [<ffffffff81054210>] ? kthread_create_on_node+0x180/0x180
[   78.564755] ---[ end trace 8b0d943af76d3736 ]---

This warning is not critical and has only been placed in the code to
actually catch this exact situation. To avoid triggering it move
the smp_unregister() into hci_dev_do_close() which will now also
take care of remove the SMP channel. It is safe to call this function
since it only remove the channel if it has been previously registered.
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>