BaseTools: Fix VPD PCD Sub-section display bug

BaseTools: Fix VPD PCD Sub-section display bug

original we get the VPD PCD items from the VPDGuid.map file in the FV
output folder. but this logic doesn't work when 1) there only have
single non Default SKU, 2) there have multiple SKU with same value.
Now we change it to get the really VPD Pcd items that already display
in the PCD section of the report.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Yonghong Zhu <yonghong.zhu@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>