net/af_packet: check len when min_header_len equals to 0

User can use AF_PACKET socket to send packets with the length of 0.
When min_header_len equals to 0, packet_snd will call __dev_queue_xmit
to send packets, and sock->type can be any type.

Reported-by:  <syzbot+5ea725c25d06fb9114c4@syzkaller.appspotmail.com>
Fixes: fd189422 ("bpf: Don't redirect packets with invalid pkt_len")
Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>