ACPICA: Add exception descriptions to exception info table

Descriptions to be compiled/used by the acpihelp utility only. Not
compiled for the kernel ACPICA code.

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>