net: hns3: free the pending skb when clean RX ring

If there is pending skb in RX flow when close the port, and the
pending buffer is not cleaned, the new packet will be added to
the pending skb when the port opens again, and the first new
packet has error data.

This patch cleans the pending skb when clean RX ring.

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