UefiCpuPkg/RegisterCpuFeaturesLib: Simplify PcdCpuFeaturesSupport.

UefiCpuPkg/RegisterCpuFeaturesLib: Simplify PcdCpuFeaturesSupport.

PcdCpuFeaturesSupport used to specify the platform policy about
what CPU features this platform supports. This PCD will be used
in IsCpuFeatureSupported only.

Now RegisterCpuFeaturesLib use this PCD as an template to Get the
pcd size. Update the code logic to replace it with
PcdCpuFeaturesSetting.

BZ:https://bugzilla.tianocore.org/show_bug.cgi?id=1375

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Eric Dong <eric.dong@intel.com>
Reviewed-by: Ray Ni <ray.ni@intel.com>