In FatPkg, cluster-related varibles are declared as unsigned type (e.g. UINT32/UINTN). To keep the comparisions involving those variables type-matched, declare the definition FAT_CLUSTER_SPECIAL as unsigned type explicitly. Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Hao Wu <hao.a.wu@intel.com> Reviewed-by: Ruiyu Ni <ruiyu.ni@intel.com>