iwlwifi: clear up AC/FIFO debug output

Not all queues are mapped for frame transmission,
so saying "AC" is misleading. They are all mapped
to FIFOs, obviously, though, so use that term and
also say AC/CMD instead of just AC for the queue
type.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>