be2net: bug fix in be_change_mtu

Current code allows the new mtu to cross the supported value.
This patch fixes the boundary checks.

From: Suresh R <sureshr@serverengines.com>
Signed-off-by: Ajit Khaparde <ajitk@serverengines.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/benet/be_main.c

@@ -473,10 +473,12 @@ static int be_change_mtu(struct net_device *netdev, int new_mtu)
 {
 	struct be_adapter *adapter = netdev_priv(netdev);
 	if (new_mtu < BE_MIN_MTU ||
-			new_mtu > BE_MAX_JUMBO_FRAME_SIZE) {
+			new_mtu > (BE_MAX_JUMBO_FRAME_SIZE -
+					(ETH_HLEN + ETH_FCS_LEN))) {
 		dev_info(&adapter->pdev->dev,
 			"MTU must be between %d and %d bytes\n",
-			BE_MIN_MTU, BE_MAX_JUMBO_FRAME_SIZE);
+			BE_MIN_MTU,
+			(BE_MAX_JUMBO_FRAME_SIZE - (ETH_HLEN + ETH_FCS_LEN)));
 		return -EINVAL;
 	}
 	dev_info(&adapter->pdev->dev, "MTU changed from %d to %d bytes\n",