ipw2x00: remove set but not used variable 'force_update'

Fixes gcc '-Wunused-but-set-variable' warning:

drivers/net/wireless/intel/ipw2x00/ipw2100.c: In function shim__set_security:
drivers/net/wireless/intel/ipw2x00/ipw2100.c:5582:9: warning: variable force_update set but not used [-Wunused-but-set-variable]
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: zhengbin <zhengbin13@huawei.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/intel/ipw2x00/ipw2100.c

@@ -5565,7 +5565,7 @@ static void shim__set_security(struct net_device *dev,
 			       struct libipw_security *sec)
 {
 	struct ipw2100_priv *priv = libipw_priv(dev);
-	int i, force_update = 0;
+	int i;
 
 	mutex_lock(&priv->action_mutex);
 	if (!(priv->status & STATUS_INITIALIZED))
@@ -5605,7 +5605,6 @@ static void shim__set_security(struct net_device *dev,
 		priv->ieee->sec.flags |= SEC_ENABLED;
 		priv->ieee->sec.enabled = sec->enabled;
 		priv->status |= STATUS_SECURITY_UPDATED;
-		force_update = 1;
 	}
 
 	if (sec->flags & SEC_ENCRYPT)