iwlegacy: add il_{stop,wake}_queues_by_reason functions

Add functions that will stop/wake all queues. Make them safe
regarding multiple calls and when some ac are stopped/woke
independently.

Tested-by: Jake Edge <jake@lwn.net>
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>