lan78xx: Limit number of driver warning messages

Device removal can result in a large burst of driver warning messages
(20 - 30) sent to the kernel log. Most of these are register read/write
failures.

This change limits the rate at which these messages are emitted.
Signed-off-by: John Efstathiades <john.efstathiades@pebblebay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/usb/lan78xx.c

@@ -462,7 +462,7 @@ static int lan78xx_read_reg(struct lan78xx_net *dev, u32 index, u32 *data)
 	if (likely(ret >= 0)) {
 		le32_to_cpus(buf);
 		*data = *buf;
-	} else {
+	} else if (net_ratelimit()) {
 		netdev_warn(dev->net,
 			    "Failed to read register index 0x%08x. ret = %d",
 			    index, ret);
@@ -492,7 +492,8 @@ static int lan78xx_write_reg(struct lan78xx_net *dev, u32 index, u32 data)
 			      USB_VENDOR_REQUEST_WRITE_REGISTER,
 			      USB_DIR_OUT | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
 			      0, index, buf, 4, USB_CTRL_SET_TIMEOUT);
-	if (unlikely(ret < 0)) {
+	if (unlikely(ret < 0) &&
+	    net_ratelimit()) {
 		netdev_warn(dev->net,
 			    "Failed to write register index 0x%08x. ret = %d",
 			    index, ret);