UefiCpuPkg/S3Resume2Pei: Handle Communicate Ppi not exist issue.

UefiCpuPkg/S3Resume2Pei: Handle Communicate Ppi not exist issue.

Current code assume Communicate Ppi always existed, so it adds
ASSERT to confirm it. Ovmf platform happened not has this Ppi, so
the ASSERT been trig. This patch handle Ppi not existed case.

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