acpi: Create subtable parsing infrastructure

Parsing entries in an ACPI table had assumed a generic header
structure. There is no standard ACPI header, though, so less common
layouts with different field sizes required custom parsers to go through
their subtable entry list.

Create the infrastructure for adding different table types so parsing
the entries array may be more reused for all ACPI system tables and
the common code doesn't need to be duplicated.

Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Tested-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Keith Busch <keith.busch@intel.com>
Tested-by: Brice Goglin <Brice.Goglin@inria.fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/acpi/scan.c

@@ -2241,10 +2241,10 @@ static struct acpi_probe_entry *ape;
 static int acpi_probe_count;
 static DEFINE_MUTEX(acpi_probe_mutex);
 
-static int __init acpi_match_madt(struct acpi_subtable_header *header,
+static int __init acpi_match_madt(union acpi_subtable_headers *header,
 				  const unsigned long end)
 {
-	if (!ape->subtable_valid || ape->subtable_valid(header, ape))
+	if (!ape->subtable_valid || ape->subtable_valid(&header->common, ape))
 		if (!ape->probe_subtbl(header, end))
 			acpi_probe_count++;