net/sun3_82586: fix potential memory leak in sun3_82586_send_packet()

The sun3_82586_send_packet() returns NETDEV_TX_OK without freeing skb
in case of skb->len being too long, add dev_kfree_skb() to fix it.

Fixes: 1da177e4 ("Linux-2.6.12-rc2")
Signed-off-by: Wang Hai <wanghai38@huawei.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Message-ID: <20241015144148.7918-1-wanghai38@huawei.com>
Signed-off-by: Andrew Lunn <andrew@lunn.ch>