Make the error message clearer if fail to get ACPI/FPDT table. Cc: Liming Gao <liming.gao@intel.com> Cc: Jiewen Yao <jiewen.yao@intel.com> Contributed-under: TianoCore Contribution Agreement 1.1 Signed-off-by: Dandan Bi <dandan.bi@intel.com> Reviewed-by: Liming Gao <liming.gao@intel.com>