iwmc3200wifi: fix potential kernel oops on module removal

The iwm_if_free() is called before destroy_workqueue for isr_wq on
device remove method. But if there is still some pending work in
the isr_wq, the required data structures are already freed at this
point. This leeds a kernel oops. The patch fixes this problem by
moving iwm_if_free after destroy_workqueue.
Signed-off-by: NZhu Yi <yi.zhu@intel.com>
Signed-off-by: NSamuel Ortiz <samuel.ortiz@intel.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

drivers/net/wireless/iwmc3200wifi/sdio.c

@@ -479,10 +479,10 @@ static void iwm_sdio_remove(struct sdio_func *func)
 	struct iwm_priv *iwm = hw_to_iwm(hw);
 	struct device *dev = &func->dev;
 
-	iwm_debugfs_exit(iwm);
 	iwm_if_remove(iwm);
-	iwm_if_free(iwm);
 	destroy_workqueue(hw->isr_wq);
+	iwm_debugfs_exit(iwm);
+	iwm_if_free(iwm);
 
 	sdio_set_drvdata(func, NULL);