net: hns: Clean redundant code from hns_mdio.c file

This patch cleans the redundant code from  hns_mdio.c.

Reported-by: Ping Zhang <zhangping5@huawei.com>
Signed-off-by: Kejian Yan <yankejian@huawei.com>
Reviewed-by: Salil Mehta <salil.mehta@huawei.com>
Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>