Use PcdSpeculationBarrierType in the x86 implementation of SpeculationBarrier() to select between AsmLfence(), AsmCpuid(), and no operation. Cc: Liming Gao <liming.gao@intel.com> Signed-off-by: Michael D Kinney <michael.d.kinney@intel.com> Reviewed-by: Laszlo Ersek <lersek@redhat.com> Reviewed-by: Brian J. Johnson <brian.johnson@hpe.com>