net: hisilicon: deals with the sub ctrl by syscon

the global Soc configuration is treated by syscon, and sub ctrl bus is
Soc bus. it has to be treated by syscon.

Signed-off-by: yankejian <yankejian@huawei.com>
Signed-off-by: lisheng <lisheng011@huawei.com>
Signed-off-by: lipeng <lipeng321@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>