ACPICA: ACPI 6.4: MADT: add Multiprocessor Wakeup Mailbox Structure

ACPICA commit f1ee04207a212f6c519441e7e25397649ebc4cea

Add Multiprocessor Wakeup Mailbox Structure definition. It is useful
in parsing MADT Wake table.

Link: https://github.com/acpica/acpica/commit/f1ee0420


Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Erik Kaneda <erik.kaneda@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>