macvlan: implement .parse_protocol hook function in macvlan_hard_header_ops

macvlan: implement .parse_protocol hook function in macvlan_hard_header_ops

The .parse_protocol hook function in the macvlan_header_ops structure is
not implemented. As a result, when the AF_PACKET family is used to send
packets, skb->protocol will be set to 0.
Macvlan is a device of type ARPHRD_ETHER (ether_setup). Therefore, use
eth_header_parse_protocol function to obtain the protocol.

Suggested-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://lore.kernel.org/r/20231202130658.2266526-1-shaozhengchao@huawei.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>