net: hns: Clean rx fbd when ae stopped.

If there are packets in hardware when changing the speed or duplex,
it may cause hardware hang up.

This patch adds the code to wait rx fbd clean up when ae stopped.

Signed-off-by: Yonglong Liu <liuyonglong@huawei.com>
Signed-off-by: Peng Li <lipeng321@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>