Revert "usb: gadget: NCM: Protect dev->port_usb using dev->lock"

This reverts commit c9ffc78745f89e300fe704348dd8e6800acf4d18 as it was
reported to be broken.

Cc: Felipe Balbi <felipe.balbi@linux.intel.com>
Cc: Jim Baxter <jim_baxter@mentor.com>
Cc: Harish Jenny K N <harish_kandiga@mentor.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/gadget/function/u_ether.c

@@ -553,16 +553,14 @@ static netdev_tx_t eth_start_xmit(struct sk_buff *skb,
 		spin_lock_irqsave(&dev->lock, flags);
 		if (dev->port_usb)
 			skb = dev->wrap(dev->port_usb, skb);
+		spin_unlock_irqrestore(&dev->lock, flags);
 		if (!skb) {
 			/* Multi frame CDC protocols may store the frame for
 			 * later which is not a dropped frame.
 			 */
 			if (dev->port_usb &&
-					dev->port_usb->supports_multi_frame) {
-				spin_unlock_irqrestore(&dev->lock, flags);
+					dev->port_usb->supports_multi_frame)
 				goto multiframe;
-			}
-			spin_unlock_irqrestore(&dev->lock, flags);
 			goto drop;
 		}
 	}
@@ -580,7 +578,6 @@ static netdev_tx_t eth_start_xmit(struct sk_buff *skb,
 		req->zero = 0;
 	else
 		req->zero = 1;
-	spin_unlock_irqrestore(&dev->lock, flags);
 
 	/* use zlp framing on tx for strict CDC-Ether conformance,
 	 * though any robust network rx path ignores extra padding.