UefiCpuPkg/CommonFeature: Skip locking when the feature is disabled

UefiCpuPkg/CommonFeature: Skip locking when the feature is disabled

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=1305

Today's code unconditionally sets the IA32_FEATURE_CONTROL.Lock to 1
no matter the feature is enabled or not.

The patch fixes this issue by only setting the Lock bit to 1 when
the feature is enabled.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com>
Reviewed-by: Eric Dong <eric.dong@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>