net: hns3: fix for fraglist SKB headlen not handling correctly

When the fraglist SKB headlen is larger than zero, current code
still handle the fraglist SKB linear data as frag data, which may
cause TX error.

This patch adds a new DESC_TYPE_FRAGLIST_SKB type to handle the
mapping and unmapping of the fraglist SKB linear data buffer.

Fixes: 8ae10cfb

 ("net: hns3: support tx-scatter-gather-fraglist feature")
Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
Signed-off-by: Huazhong Tan <tanhuazhong@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>