ACPICA: Fix for LoadTable operator, input strings

Fixed a problem with the LoadTable operator where the OemId
and OemTableId input strings could cause unexpected failures if
they were shorter than the maximum lengths allowed.

http://www.acpica.org/bugzilla/show_bug.cgi?id=576

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