ethernet/marvell: use core min/max MTU checking

mvneta: min_mtu 68, max_mtu 9676
- mtu validation routine mostly did range check, merge back into
  mvneta_change_mtu for simplicity

mvpp2: min_mtu 68, max_mtu 9676
- mtu validation routine mostly did range check, merge back into
  mvpp2_change_mtu for simplicity

pxa168_eth: min_mtu 68, max_mtu 9500

skge: min_mtu 60, max_mtu 9000

sky2: min_mtu 68, max_mtu 1500 or 9000, depending on hw

CC: netdev@vger.kernel.org
CC: Mirko Lindner <mlindner@marvell.com>
CC: Stephen Hemminger <stephen@networkplumber.org>
CC: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Jarod Wilson <jarod@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/marvell/skge.c

@@ -2900,9 +2900,6 @@ static int skge_change_mtu(struct net_device *dev, int new_mtu)
 {
 	int err;
 
-	if (new_mtu < ETH_ZLEN || new_mtu > ETH_JUMBO_MTU)
-		return -EINVAL;
-
 	if (!netif_running(dev)) {
 		dev->mtu = new_mtu;
 		return 0;
@@ -3857,6 +3854,10 @@ static struct net_device *skge_devinit(struct skge_hw *hw, int port,
 	dev->watchdog_timeo = TX_WATCHDOG;
 	dev->irq = hw->pdev->irq;
 
+	/* MTU range: 60 - 9000 */
+	dev->min_mtu = ETH_ZLEN;
+	dev->max_mtu = ETH_JUMBO_MTU;
+
 	if (highmem)
 		dev->features |= NETIF_F_HIGHDMA;