BaseTools: Fix a bug override Pcd by DSC Components section

BaseTools: Fix a bug override Pcd by DSC Components section

The case is: define a VOID* pcd in DEC file, eg: Value is {0x1}.
then override this PCD on DSC component section, eg: Value is
{0x1, 0x2, 0x3}, the max size of this PCD is calculate wrong
which cause build error.

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