net/hns3: disable PFC if not configured

net/hns3: disable PFC if not configured

If "dcb_capability_en" in "data->dev_conf" delivered from the dev_configure
does not have the ETH_DCB_PFC_SUPPORT flag, the user wants to disable PFC,
and only enable ETS. Therefore, this patch supports the function of
disabling PFC by the field. In addition, this patch updates
"current_fc_status" of the driver based on the flow control mode requested
by user so as to enable the flow control mode in multi-TC scenarios.

Signed-off-by: Huisong Li <lihuisong@huawei.com>
Signed-off-by: Min Hu (Connor) <humin29@huawei.com>