net: ethernet: aeroflex: fix potential memory leak in greth_start_xmit_gbit()

The greth_start_xmit_gbit() returns NETDEV_TX_OK without freeing skb
in case of skb->len being too long, add dev_kfree_skb() to fix it.

Fixes: d4c4113 ("net: Add Aeroflex Gaisler 10/100/1G Ethernet MAC driver")
Signed-off-by: Wang Hai <wanghai38@huawei.com>
Reviewed-by: Gerhard Engleder <gerhard@engleder-embedded.com>
Link: https://patch.msgid.link/20241012110434.49265-1-wanghai38@huawei.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: Wang Hai

drivers/net/ethernet/aeroflex/greth.c

@@ -484,7 +484,7 @@ greth_start_xmit_gbit(struct sk_buff *skb, struct net_device *dev)
 
 	if (unlikely(skb->len > MAX_FRAME_SIZE)) {
 		dev->stats.tx_errors++;
-		goto out;
+		goto len_error;
 	}
 
 	/* Save skb pointer. */
@@ -575,6 +575,7 @@ greth_start_xmit_gbit(struct sk_buff *skb, struct net_device *dev)
 map_error:
 	if (net_ratelimit())
 		dev_warn(greth->dev, "Could not create TX DMA mapping\n");
+len_error:
 	dev_kfree_skb(skb);
 out:
 	return err;