net: hns3: Fix for waterline not setting correctly

The HCLGE_RX_PRIV_EN_B is used to tell the firmware whether
to update the specific waterline value, if the is not set,
the firmware will ignore the value.

This patch fixes by setting the HCLGE_RX_PRIV_EN_B even if
the updated value is zero.

Fixes: 46a3df9f ("net: hns3: Add HNS3 Acceleration Engine & Compatibility Layer Support")
Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
Signed-off-by: Peng Li <lipeng321@huawei.com>
Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>