when only define the PCD in the DEC file, and use --pcd feature,
we also need cover this case for Feature Flag Type.
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Yonghong Zhu <yonghong.zhu@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>