rndis_wlan: check if set_multicast_list work is already scheduled

Don't queue set_multicast_list work if WORK_SET_MULTICAST_LIST
flag already set.

Signed-off-by: Jussi Kivilinna <jussi.kivilinna@mbnet.fi>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/rndis_wlan.c b/drivers/net/wireless/rndis_wlan.c
index c281c0b..ad46a0b 100644
--- a/drivers/net/wireless/rndis_wlan.c
+++ b/drivers/net/wireless/rndis_wlan.c
@@ -2272,6 +2272,9 @@
 	struct usbnet *usbdev = dev->priv;
 	struct rndis_wext_private *priv = get_rndis_wext_priv(usbdev);
 
+	if (test_bit(WORK_SET_MULTICAST_LIST, &priv->work_pending))
+		return;
+
 	set_bit(WORK_SET_MULTICAST_LIST, &priv->work_pending);
 	queue_work(priv->workqueue, &priv->work);
 }