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