BaseTools: Fixed some small issues
    1. The structure pcd default value should use the default value under sku.
    2. Incorrect VpdOffset value for those un-used in module Vpd
    3. Add a checkpoint for Structure Pcd Name
    
    Contributed-under: TianoCore Contribution Agreement 1.1
    Signed-off-by: Bob Feng <bob.c.feng@intel.com>
    Cc: Liming Gao <liming.gao@intel.com>
    Reviewed-by: Liming Gao <liming.gao@intel.com>