UefiCpuPkg/MpInitLib: Set new AP to idle state after switching BSP

We need to set new AP to idle state if it is expected to be waken up by new BSP
later.

Cc: Feng Tian <feng.tian@intel.com>
Cc: Kinney Michael D <michael.d.kinney@intel.com>
Cc: Ruiyu Ni <ruiyu.ni@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.c

@@ -1608,6 +1608,8 @@ SwitchBSPWorker (
   //
   if (!EnableOldBSP) {
     SetApState (&CpuMpData->CpuData[CallerNumber], CpuStateDisabled);
+  } else {
+    SetApState (&CpuMpData->CpuData[CallerNumber], CpuStateIdle);
   }
   //
   // Save new BSP number