iwlwifi: use singlethread workqueue

Use one workqueue instead of one per CPU.

Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
cc: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

diff --cc drivers/net/wireless/iwlwifi/iwl-agn.c
Simple merge

diff --cc drivers/net/wireless/iwlwifi/iwl3945-base.c
Simple merge