UefiCpuPkg/RegisterCpuFeaturesLib: avoid use dynamic PCD.

UefiCpuPkg/RegisterCpuFeaturesLib: avoid use dynamic PCD.

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=1972

Function in this library may be used by APs. Assert will be trig if AP
uses dynamic pcd.
This patch enhance the current code, remove the unnecessary usage of
dynamic PCD. This change try to avoid report this issue again later.

Cc: Ray Ni <ray.ni@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Chandana Kumar <chandana.c.kumar@intel.com>
Cc: Star Zeng <star.zeng@intel.com>
Signed-off-by: Eric Dong <eric.dong@intel.com>
Reviewed-by: Ray Ni <ray.ni@intel.com>
Reviewed-by: Star Zeng <star.zeng@intel.com>