hisi_sas: use Unified Device Properties API

The hisi_sas driver is required to support both device tree and
ACPI. The scanning of the device properties now uses the Unified Device
Properties API, which serves both OF and ACPI.

Since syscon is not supported by ACPI, syscon is only used in the driver
when device tree is used.

Signed-off-by: John Garry <john.garry@huawei.com>
Signed-off-by: Zhangfei Gao <zhangfei.gao@linaro.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>