net: usb: kaweth: use irqsave() in USB's complete callback

The USB completion callback does not disable interrupts while acquiring
the lock. We want to remove the local_irq_disable() invocation from
__usb_hcd_giveback_urb() and therefore it is required for the callback
handler to disable the interrupts while acquiring the lock.
The callback may be invoked either in IRQ or BH context depending on the
USB host controller.
Use the _irqsave() variant of the locking primitives.

Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: NSebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/usb/kaweth.c

@@ -587,7 +587,7 @@ static void kaweth_usb_receive(struct urb *urb)
 	struct kaweth_device *kaweth = urb->context;
 	struct net_device *net = kaweth->net;
 	int status = urb->status;
-
+	unsigned long flags;
 	int count = urb->actual_length;
 	int count2 = urb->transfer_buffer_length;
 
@@ -619,12 +619,12 @@ static void kaweth_usb_receive(struct urb *urb)
 		net->stats.rx_errors++;
 		dev_dbg(dev, "Status was -EOVERFLOW.\n");
 	}
-	spin_lock(&kaweth->device_lock);
+	spin_lock_irqsave(&kaweth->device_lock, flags);
 	if (IS_BLOCKED(kaweth->status)) {
-		spin_unlock(&kaweth->device_lock);
+		spin_unlock_irqrestore(&kaweth->device_lock, flags);
 		return;
 	}
-	spin_unlock(&kaweth->device_lock);
+	spin_unlock_irqrestore(&kaweth->device_lock, flags);
 
 	if(status && status != -EREMOTEIO && count != 1) {
 		dev_err(&kaweth->intf->dev,