net: hns3: fix "tc qdisc del" failed issue

The HNS3 driver supports to configure TC numbers and TC to priority
map via "tc" tool. But when delete the rule, will fail, because
the HNS3 driver needs at least one TC, but the "tc" tool sets TC
number to zero when delete.

This patch makes sure that the TC number is at least one.

Fixes: 30d240df ("net: hns3: Add mqprio hardware offload support in hns3 driver")
Signed-off-by: Yonglong Liu <liuyonglong@huawei.com>
Signed-off-by: Huazhong Tan <tanhuazhong@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>