net/hns3: fix flushing RSS rule

net/hns3: fix flushing RSS rule

When user create a flow without RSS by calling rte_flow_create API and then
destroy it by calling rte_flow_flush API, driver should not clear RSS rule.

A reasonable handling method is that when user creates an RSS rule, the
driver should clear the created RSS rule when flushing destroy all flow
rules. Also, hw->rss_info should save the RSS config of the last success
RSS rule. When create n RSS rules, the RSS should not be disabled before
the last RSS rule destroyed.

Fixes: c37ca66f2b27 ("net/hns3: support RSS")
Cc: stable@dpdk.org
Signed-off-by: Lijun Ou <oulijun@huawei.com>
Signed-off-by: Wei Hu (Xavier) <xavier.huwei@huawei.com>