UefiCpuPkg/MpInitLib: Update AP information when BSP switched

When BSP switched, we need to update some AP information. For example,
ApStartupSignalBuffer and ApTopOfStack.

Cc: Feng Tian <feng.tian@intel.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jeff Fan <jeff.fan@intel.com>
Reviewed-by: Feng Tian <feng.tian@intel.com>

UefiCpuPkg/Library/MpInitLib/MpLib.h

@@ -216,6 +216,7 @@ struct _CPU_MP_DATA {
   AP_INIT_STATE                  InitFlag;
   BOOLEAN                        X2ApicEnable;
   BOOLEAN                        SwitchBspFlag;
+  UINTN                          NewBspNumber;
   CPU_EXCHANGE_ROLE_INFO         BSPInfo;
   CPU_EXCHANGE_ROLE_INFO         APInfo;
   MTRR_SETTINGS                  MtrrTable;