UefiCpuPkg: Use Top of each AP's stack to save CpuMpData

To remove the dependency of CPU register, 4/8 byte at the top of the
stack is occupied for CpuMpData. BIST information is also taken care
here. This modification is only for PEI phase, since in DXE phase
CpuMpData is accessed via global variable.

Signed-off-by: Yuanhao Xie <yuanhao.xie@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Reviewed-by: Ray Ni <ray.ni@intel.com>
Cc: Rahul Kumar <rahul1.kumar@intel.com>

UefiCpuPkg/Library/MpInitLib/MpLib.h

@@ -301,6 +301,14 @@ struct _CPU_MP_DATA {
   UINT64         GhcbBase;
 };
 
+//
+// AP_STACK_DATA is stored at the top of each AP stack.
+//
+typedef struct {
+  UINTN          Bist;
+  CPU_MP_DATA    *MpData;
+} AP_STACK_DATA;
+
 #define AP_SAFE_STACK_SIZE   128
 #define AP_RESET_STACK_SIZE  AP_SAFE_STACK_SIZE