kernel: drivers: net: usbnet: Fix -Wcast-function-type

correct usage prototype of callback in tasklet_init().
Report by KSPP#20

Signed-off-by: Phong Tran <tranmanphong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Fix from upstream: 2eb1d3f4bc

release/src-rt-7.x.main/src/linux/linux-2.6.36/drivers/net/usb/usbnet.c

@@ -1542,6 +1542,12 @@ static void usbnet_bh (unsigned long param)
 	}
 }
 
+static void usbnet_bh_tasklet(unsigned long data)
+{
+	struct timer_list *t = (struct timer_list *)data;
+
+	usbnet_bh(t);
+}
 
 /*-------------------------------------------------------------------------
  *
@@ -1662,7 +1668,7 @@ usbnet_probe (struct usb_interface *udev, const struct usb_device_id *prod)
 	skb_queue_head_init (&dev->txq);
 	skb_queue_head_init (&dev->done);
 	skb_queue_head_init(&dev->rxq_pause);
-	dev->bh.func = usbnet_bh;
+	dev->bh.func = usbnet_bh_tasklet;
 	dev->bh.data = (unsigned long) dev;
 	INIT_WORK (&dev->kevent, usbnet_deferred_kevent);
 	init_usb_anchor(&dev->deferred);