ACPICA: Never run _REG on system_memory and system_IO

These address spaces are defined by the ACPI spec to be
"always available", and thus _REG should never be run on them.
Provides compatibility with other ACPI implementations.

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