UefiCpuPkg: CpuIo2Smm: Support of CpuIo driver under StandaloneMm

UefiCpuPkg: CpuIo2Smm: Support of CpuIo driver under StandaloneMm

This change adds a new CpuIo driver instance for MM_STANDALONE type. The
new driver entrypoint is implemented in a separate file to match the
interface definition of MM_STANDALONE modules.

Cc: Eric Dong <eric.dong@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Rahul Kumar <rahul1.kumar@intel.com>
Signed-off-by: Kun Qin <kun.q@outlook.com>
Reviewed-by: Ray Ni <ray.ni@intel.com>