net: hns3: add tm flush when setting tm

When the tm module is configured with traffic, traffic
may be abnormal. This patch fixes this problem.
Before the tm module is configured, traffic processing
should be stopped. After the tm module is configured,
traffic processing is enabled.

Signed-off-by: Hao Lan <lanhao@huawei.com>
Signed-off-by: Jijie Shao <shaojijie@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>