ACPICA: Module-level code: enable _REG execution in same scope

This change enables the execution of _REG methods that appear
in the same scope as the module-level code, in resonse to an
operation region declaration within the module-level code.

Signed-off-by: Lin Ming <ming.m.lin@intel.com>
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>