OvmfPkg/PlatformPei: create one memory HOB at S3 resume too, for CpuMpPei

OvmfPkg/PlatformPei: create one memory HOB at S3 resume too, for CpuMpPei

CpuMpPei will have to place the AP startup vector in memory under 1MB. For
this, CpuMpPei borrows memory under 1MB, but it needs a memory resource
descriptor HOB to exist there even on the S3 resume path (see the
GetWakeupBuffer() function). Produce such a HOB as an exception on the S3
resume path.

CpuMpPei is going be dispatched no earlier than PlatformPei, because
CpuMpPei has a depex on gEfiPeiMemoryDiscoveredPpiGuid, and PlatformPei
calls PublishSystemMemory().

Cc: Jeff Fan <jeff.fan@intel.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Michael Kinney <michael.d.kinney@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Jeff Fan <jeff.fan@intel.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>