firewire: ohci: flush AT contexts after bus reset - addendum

Add comments
  - on why bus_reset_tasklet flushes AT queues,
  - that commit 76f73ca1 can possibly be reverted now.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Acked-by: Jarod Wilson <jarod@redhat.com>