net: hns3: add limit ets dwrr bandwidth cannot be 0

net: hns3: add limit ets dwrr bandwidth cannot be 0

If ets dwrr bandwidth of tc is set to 0, the hardware will switch to SP
mode. In this case, this tc may occupy all the tx bandwidth if it has
huge traffic, so it violates the purpose of the user setting.

To fix this problem, limit the ets dwrr bandwidth must greater than 0.

Fixes: cacde272dd00 ("net: hns3: Add hclge_dcb module for the support of DCB feature")
Signed-off-by: Guangbin Huang <huangguangbin2@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>