sata: xgene: add ACPI support for APM X-Gene SATA ports

This adds ACPI support for the APM X-Gene SATA ports. When the system
boots using ACPI table, the SATA ports are able to configure using the
values supplied by the ACPI table rather than the DTS.

Signed-off-by: Feng Kan <fkan@apm.com>
Reviewed-by: Hanjun Guo <hanjun.guo@linaro.org>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Tejun Heo <tj@kernel.org>