net: hns3: add support for querying pfc puase packets statistic

This patch add support for querying pfc puase packets statistic
in hclge_ieee_getpfc, which is used to tell user how many pfc
puase packets have been sent and received by this mac port.

Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
Signed-off-by: Peng Li <lipeng321@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>