net: hns: get reset registers from DT

Since the registers of subctrl may be different, it is better to
mv the registers from hns mdio driver routine to device tree node.

Signed-off-by: Kejian Yan <yankejian@huawei.com>
Signed-off-by: Yisen Zhuang <Yisen.Zhuang@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>