usb: gadget: u_ether: remove interrupt throttling

According to Dave Miller "the networking stack has a
hard requirement that all SKBs which are transmitted
must have their completion signalled in a fininte
amount of time. This is because, until the SKB is
freed by the driver, it holds onto socket,
netfilter, and other subsystem resources."

In summary, this means that using TX IRQ throttling
for the networking gadgets is, at least, complex and
we should avoid it for the time being.

Cc: <stable@vger.kernel.org>
Reported-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Tested-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Suggested-by: NDavid Miller <davem@davemloft.net>
Signed-off-by: NFelipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/gadget/function/u_ether.c

@@ -588,14 +588,6 @@ static netdev_tx_t eth_start_xmit(struct sk_buff *skb,
 
 	req->length = length;
 
-	/* throttle high/super speed IRQ rate back slightly */
-	if (gadget_is_dualspeed(dev->gadget))
-		req->no_interrupt = (((dev->gadget->speed == USB_SPEED_HIGH ||
-				       dev->gadget->speed == USB_SPEED_SUPER)) &&
-					!list_empty(&dev->tx_reqs))
-			? ((atomic_read(&dev->tx_qlen) % dev->qmult) != 0)
-			: 0;
-
 	retval = usb_ep_queue(in, req, GFP_ATOMIC);
 	switch (retval) {
 	default: