Update LIBRARY_CLASS of BaseCpuTimerLib to remove the usage limitation,
otherwise the Base instance cannot be used in some types of modules.
Signed-off-by: Jason Lou <yun.lou@intel.com> Reviewed-by: Ray Ni <ray.ni@intel.com> Cc: Eric Dong <eric.dong@intel.com> Cc: Laszlo Ersek <lersek@redhat.com> Cc: Rahul Kumar <rahul1.kumar@intel.com>