BaseTools: Don't save unused workspace data

BaseTools: Don't save unused workspace data

  FlexibleFieldName was never used not set.
  DefinitionPosition (file and line number) are recalculated
and never used outside the function.  remove the saving of the
data.

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