wireless: Remove redundant 'flush_workqueue()' calls

'destroy_workqueue()' already drains the queue before destroying it, so
there is no need to flush it explicitly.

Remove the redundant 'flush_workqueue()' calls.

This was generated with coccinelle:

@@
expression E;
@@
- 	flush_workqueue(E);
	destroy_workqueue(E);

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/0855d51423578ad019c0264dad3fe47a2e8af9c7.1633849511.git.christophe.jaillet@wanadoo.fr

drivers/net/wireless/intel/iwlegacy/3945-mac.c

@@ -3819,7 +3819,6 @@ il3945_pci_remove(struct pci_dev *pdev)
 	il3945_unset_hw_params(il);
 
 	/*netif_stop_queue(dev); */
-	flush_workqueue(il->workqueue);
 
 	/* ieee80211_unregister_hw calls il3945_mac_stop, which flushes
 	 * il->workqueue... so we can't take down the workqueue

drivers/net/wireless/intel/iwlegacy/4965-mac.c

@@ -6731,7 +6731,6 @@ il4965_pci_remove(struct pci_dev *pdev)
 	il_eeprom_free(il);
 
 	/*netif_stop_queue(dev); */
-	flush_workqueue(il->workqueue);
 
 	/* ieee80211_unregister_hw calls il_mac_stop, which flushes
 	 * il->workqueue... so we can't take down the workqueue

drivers/net/wireless/intel/iwlwifi/dvm/main.c

@@ -1525,7 +1525,6 @@ static void iwl_op_mode_dvm_stop(struct iwl_op_mode *op_mode)
 	kfree(priv->nvm_data);
 
 	/*netif_stop_queue(dev); */
-	flush_workqueue(priv->workqueue);
 
 	/* ieee80211_unregister_hw calls iwlagn_mac_stop, which flushes
 	 * priv->workqueue... so we can't take down the workqueue