Bluetooth: Remove unnecessary hci_dev_unlock for smp_user_confirm_reply

Now that the SMP context has it's own crypto handle it doesn't need to
lock the hci_dev anymore for most operations. This means that it is safe
to call smp_user_confirm_reply with the lock already held.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>