ACPICA: iASL: add new OperationRegion subtype keyword PlatformRtMechanism

ACPICA commit 2c2eefa827bd37297f5f9ca4b263fcba829aaf3f

Link: https://github.com/acpica/acpica/commit/2c2eefa8


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