net: hns3: fix for not calculating tx bd num correctly

When there is only one byte in a frag, the current calculation
using "(size + HNS3_MAX_BD_SIZE - 1) >> HNS3_MAX_BD_SIZE_OFFSET"
will return zero, because HNS3_MAX_BD_SIZE is 65535 and
HNS3_MAX_BD_SIZE_OFFSET is 16. So it will cause tx error when
a frag's size is one byte.

This patch fixes it by using DIV_ROUND_UP.

Fixes: 3fe13ed9 ("net: hns3: avoid mult + div op in critical data path")
Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>