The bcmasp_xmit() returns NETDEV_TX_OK without freeing skb
in case of mapping fails, add dev_kfree_skb() to fix it.

Fixes: 490cb412 ("net: bcmasp: Add support for ASP2.0 Ethernet controller")
Signed-off-by: Wang Hai <wanghai38@huawei.com>
Acked-by: Florian Fainelli <florian.fainelli@broadcom.com>
Link: https://patch.msgid.link/20241014145901.48940-1-wanghai38@huawei.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>