ACPICA: Add "const" to some functions that return fixed strings

ACPICA commit 28645f8a113f346c8db103a4f7565fcba88c746f

Most of the "get_name" - style functions can return "const char *"
with no ill side-effects. Original linux patch from
LABBE Corentin <clabbe.montjoie@gmail.com> and backported to
ACPICA.

Link: https://github.com/acpica/acpica/commit/28645f8a


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