net/hns3: move queue stats to xstats

net/hns3: move queue stats to xstats

One of the hot discussions in community recently was moving queue stats
to xstats. In this solution, a temporary
'RTE_ETH_DEV_AUTOFILL_QUEUE_XSTATS' device flag is created to implement
the smooth switch. And the first half of this work has been completed in
the ethdev framework. Now driver needs to remove the flag from the
driver initialization process and does the rest of work.

For better readability and reasonability, per-queue stats also should be
cleared when rte_eth_stats is cleared. Otherwise, the sum of one item in
per-queue stats may be greater than corresponding item in rte_eth_stats.

Signed-off-by: Huisong Li <lihuisong@huawei.com>
Signed-off-by: Lijun Ou <oulijun@huawei.com>