ACPICA: Cleanup/improve global variable declarations.

This change cleans up the entire global variable mechaninism including
the related macros. Also reduces warnings from the "sparse" utility
in the Linux environment. Lv Zheng.

Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>