net: hns: add the code for cleaning pkt in chip

net: hns: add the code for cleaning pkt in chip

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

This patch adds the code for waiting chip to clean the all
pkts(TX & RX) in chip when the driver uses the function named
"adjust link".

This patch cleans the pkts as follows:
1) close rx of chip, close tx of protocol stack.
2) wait rcb, ppe, mac to clean.
3) adjust link
4) open rx of chip, open tx of protocol stack.

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