iwlwifi: call apm stop on exit

This patch calls apm stop on exit and suspend. Without this patch
hardware consumes power even after driver is removed or suspended.

Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Signed-off-by: Mohamed Abbas <mohamed.abbas@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>