ACPI / scan: introduce platform_id device PNP type flag

Only certain types of ACPI device objects can be enumerated as
platform devices, so in order to distinguish them from the others
introduce a new ACPI device PNP type flag, platform_id, and set it
for devices with a valid _HID to start with.

This change is based on a Zhang Rui's prototype.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>

include/acpi/acpi_bus.h

@@ -233,7 +233,8 @@ struct acpi_hardware_id {
 struct acpi_pnp_type {
 	u32 hardware_id:1;
 	u32 bus_address:1;
-	u32 reserved:30;
+	u32 platform_id:1;
+	u32 reserved:29;
 };
 
 struct acpi_device_pnp {