UefiCpuPkg/BaseUefiCpuLib.inf: Remove unnecessary library class.
    
    UefiCpuLib inf file reference itself in [LibraryClasses]
    section, this is not necessary. This patch remove it.
    
    Cc: Ruiyu Ni <ruiyu.ni@intel.com>
    Cc: Ming Shao <ming.shao@intel.com>
    Contributed-under: TianoCore Contribution Agreement 1.1
    Signed-off-by: Eric Dong <eric.dong@intel.com>
    Reviewed-by: Ruiyu Ni <ruiyu.ni@intel.com>