PcAtChipsetPkg/PcRtc: Handle NULL table entry in RSDT/XSDT
The ACPI code may reserve the first entry for a certain table
(might be FACS) to help with OS compatible issues.
We need to skip the NULL table entry in RSDT/XSDT.
Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com> Cc: Sean Brogan <sean.brogan@microsoft.com> Reviewed-by: Star Zeng <star.zeng@intel.com>