UefiCpuPkg/PiSmmCpuDxeSmm: Move S3 related code to CpuS3.c

UefiCpuPkg/PiSmmCpuDxeSmm: Move S3 related code to CpuS3.c

Cc: Jeff Fan <jeff.fan@intel.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Michael Kinney <michael.d.kinney@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Jeff Fan <jeff.fan@intel.com>
Tested-by: Laszlo Ersek <lersek@redhat.com>
Acked-by: Laszlo Ersek <lersek@redhat.com>