OvmfPkg/PlatformPei: mark cpuid and secrets memory reserved in EFI map

When SEV-SNP is active, the CPUID and Secrets memory range contains the
information that is used during the VM boot. The content need to be persist
across the kexec boot. Mark the memory range as Reserved in the EFI map
so that guest OS or firmware does not use the range as a system RAM.

Cc: Michael Roth <michael.roth@amd.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Min Xu <min.m.xu@intel.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>

OvmfPkg/PlatformPei/MemDetect.c

@@ -871,6 +871,8 @@ InitializeRamRegions (
 {
   QemuInitializeRam ();
 
+  SevInitializeRam ();
+
   if (mS3Supported && (mBootMode != BOOT_ON_S3_RESUME)) {
     //
     // This is the memory range that will be used for PEI on S3 resume