UefiCpuPkg/PiSmmCpuDxeSmm: Avoid allocate Token every time

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=2388

Token is new introduced by MM MP Protocol. Current logic allocate Token
every time when need to use it. The logic caused SMI latency raised to
very high. Update logic to allocate Token buffer at driver's entry point.
Later use the token from the allocated token buffer. Only when all the
buffer have been used, then need to allocate new buffer.

Reviewed-by: Ray Ni <ray.ni@intel.com>
Signed-off-by: Eric Dong <eric.dong@intel.com>
Acked-by: Laszlo Ersek <lersek@redhat.com>

UefiCpuPkg/UefiCpuPkg.dec

@@ -148,6 +148,10 @@
   # @Prompt Specify size of good stack of exception which need switching stack.
   gUefiCpuPkgTokenSpaceGuid.PcdCpuKnownGoodStackSize|2048|UINT32|0x30002001
 
+  ## Count of pre allocated SMM MP tokens per chunk.
+  # @Prompt Specify the count of pre allocated SMM MP tokens per chunk.
+  gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmMpTokenCountPerChunk|64|UINT32|0x30002002
+
 [PcdsFixedAtBuild, PcdsPatchableInModule]
   ## This value is the CPU Local APIC base address, which aligns the address on a 4-KByte boundary.
   # @Prompt Configure base address of CPU Local APIC