BaseTools: merge towards minimum PCD MAX <something> methods

BaseTools: merge towards minimum PCD MAX <something> methods

we have 5 different max val or max byte for PCDs.
refactor and remove 2 methods.
we need 3, as one computes for VOID* PCDs.

Cc: Bob Feng <bob.feng@intel.com>
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>