iwlwifi: fix STATUS_EXIT_PENDING is not set on pci_remove

This patch sets STATUS_EXIT_PENDING on pci_remove. Otherwise
iwl4965_down may fail to uninitialize the driver.

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>