iwlwifi: do not base station's sm_ps setting on AP

Do not use AP's SM_PS setting for our own SM_PS setting.

Reported-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>