BaseTools: Correct if condition expression for DatumType == 'VOID*'

BaseTools: Correct if condition expression for DatumType == 'VOID*'

Correct the if condition expression for DatumType == 'VOID*'. Current
this condition is not work since the DatumType is changed before we do
the value judgement.

Cc: Liming Gao <liming.gao@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Yonghong Zhu <yonghong.zhu@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>