net: hns: add support of pause frame ctrl for HNS V2

The patch adds support of pause ctrl for HNS V2, and this feature is lost
by HNS V1:
       1) service ports can disable rx pause frame,
       2) debug ports can open tx/rx pause frame.

And this patch updates the REGs about the pause ctrl when updated
status function called by upper layer routine.

Signed-off-by: Lisheng <lisheng011@huawei.com>
Signed-off-by: Yisen Zhuang <Yisen.Zhuang@huawei.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>