net: use core MTU range checking in USB NIC drivers

usbnet:
- Remove stale new_mtu <= 0 check in usbnet.c
- Set min_mtu = 0, max_mtu = 65535 (sub-drivers must set their own
  max_mtu and/or min_mtu as needed)

r8152:
- Set appropriate max_mtu for different variants (1500 or 9194)

lan78xx:
- Set max_mtu = 9000

asix_driver:
- max_mtu = 16384 for ax88178 variant

ax88179:
- max_mtu = 4088

cdc_ncm:
- max_mtu from hardware

cdc-phonet:
- min_mtu = 6, max_mtu = 65541

sierra_net:
- max_mtu = 1500, call usbnet_change_mtu directly
- sierra_net_change_mtu checked for MTU > 1500, then called
  usbnet_change_mtu, but if we set max_mtu to let the network core handle
  the range check, then we can simply call usbnet_change_mtu directly

smsc75xx:
- max_mtu = 9000

CC: netdev@vger.kernel.org
CC: Woojung Huh <woojung.huh@microchip.com>
CC: Microchip Linux Driver Support <UNGLinuxDriver@microchip.com>
CC: Hayes Wang <hayeswang@realtek.com>
CC: Oliver Neukum <oneukum@suse.com>
CC: Steve Glendinning <steve.glendinning@shawell.net>
Signed-off-by: Jarod Wilson <jarod@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/usb/r8152.c b/drivers/net/usb/r8152.c
index 8d6e13c..4213c28 100644
--- a/drivers/net/usb/r8152.c
+++ b/drivers/net/usb/r8152.c
@@ -4119,9 +4119,6 @@ static int rtl8152_change_mtu(struct net_device *dev, int new_mtu)
 		break;
 	}
 
-	if (new_mtu < 68 || new_mtu > RTL8153_MAX_MTU)
-		return -EINVAL;
-
 	ret = usb_autopm_get_interface(tp->intf);
 	if (ret < 0)
 		return ret;
@@ -4311,6 +4308,18 @@ static int rtl8152_probe(struct usb_interface *intf,
 	netdev->ethtool_ops = &ops;
 	netif_set_gso_max_size(netdev, RTL_LIMITED_TSO_SIZE);
 
+	/* MTU range: 68 - 1500 or 9194 */
+	netdev->min_mtu = ETH_MIN_MTU;
+	switch (tp->version) {
+	case RTL_VER_01:
+	case RTL_VER_02:
+		netdev->max_mtu = ETH_DATA_LEN;
+		break;
+	default:
+		netdev->max_mtu = RTL8153_MAX_MTU;
+		break;
+	}
+
 	tp->mii.dev = netdev;
 	tp->mii.mdio_read = read_mii_word;
 	tp->mii.mdio_write = write_mii_word;