net: hns3: remove some ops in struct hns3_nic_ops

The fill_desc ops has only one implementation, and
get_rxd_bnum has not been used, so this patch removes
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>