net: hns3: add tx send size handling for tso skb

The actual size on wire for tso skb should be (gso_segs - 1) *
hdr + skb->len instead of skb->len, which can be seen by user using
'ethtool -S ethX' cmd, and 'Byte Queue Limit' also use the send size
stat to do the queue limiting, so add send_bytes in the desc_cb to
record the actual send size for a skb. And send_bytes is only for tx
desc_cb and page_offset is only for rx desc, so reuse the same space
for both of them.

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>