net: cdc_ncm: set correct dev->hard_mtu

usbnet use the hard_mtu value for sizing the tx queue and nothing
else.  We will be transmitting buffers of up to tx_max size, so
that's the proper value to give usbnet.

The individual datagram size is completely irrelevant here.

Cc: Alexey Orishko <alexey.orishko@gmail.com>
Signed-off-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/usb/cdc_ncm.c

@@ -404,13 +404,6 @@ int cdc_ncm_bind_common(struct usbnet *dev, struct usb_interface *intf, u8 data_
 
 			ctx->ether_desc =
 					(const struct usb_cdc_ether_desc *)buf;
-			dev->hard_mtu =
-				le16_to_cpu(ctx->ether_desc->wMaxSegmentSize);
-
-			if (dev->hard_mtu < CDC_NCM_MIN_DATAGRAM_SIZE)
-				dev->hard_mtu =	CDC_NCM_MIN_DATAGRAM_SIZE;
-			else if (dev->hard_mtu > CDC_NCM_MAX_DATAGRAM_SIZE)
-				dev->hard_mtu =	CDC_NCM_MAX_DATAGRAM_SIZE;
 			break;
 
 		case USB_CDC_NCM_TYPE:
@@ -485,6 +478,8 @@ int cdc_ncm_bind_common(struct usbnet *dev, struct usb_interface *intf, u8 data_
 		dev_info(&dev->udev->dev, "MAC-Address: %pM\n", dev->net->dev_addr);
 	}
 
+	/* usbnet use these values for sizing tx/rx queues */
+	dev->hard_mtu = ctx->tx_max;
 	dev->rx_urb_size = ctx->rx_max;
 
 	return 0;