UefiCpuPkg/MpInitLib: Add AsmRelocateApLoop() assembly code

AsmRelocateApLoop() is used to place APs into MWAIT-loop if MonitorMwait
feature is supported before hand-off to OS, or place APs into HLT-loop if
MonitorMwait feature is not supported.

If the current mode is long mode, we will switch APs to protected mode
before placing APs in MWAIT-loop or HLT-loop. Thus, once APs wakeup from
loop, APs needn't the page table that may be crashed by OS.

v3:
  1. Rename AsmRellocateApLoop to AsmRelocateApLoop.
  2. Fix typo Proteced to Protected.
  3. Fix typo segement to segment
  4. Use word MONITOR instead of mwait-monitor.

Cc: Michael Kinney <michael.d.kinney@intel.com>
Cc: Feng Tian <feng.tian@intel.com>
Cc: Giri P Mudusuru <giri.p.mudusuru@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jeff Fan <jeff.fan@intel.com>
Reviewed-by: Giri P Mudusuru <giri.p.mudusuru@intel.com>
Reviewed-by: Michael Kinney <michael.d.kinney@intel.com>
Tested-by: Laszlo Ersek <lersek@redhat.com>
Tested-by: Michael Kinney <michael.d.kinney@intel.com>

UefiCpuPkg/Library/MpInitLib/MpLib.h

@@ -60,5 +60,26 @@ typedef struct {
 } MP_CPU_EXCHANGE_INFO;
 
 #pragma pack()
+/**
+  Assembly code to place AP into safe loop mode.
+
+  Place AP into targeted C-State if MONITOR is supported, otherwise
+  place AP into hlt state.
+  Place AP in protected mode if the current is long mode. Due to AP maybe
+  wakeup by some hardware event. It could avoid accessing page table that
+  may not available during booting to OS.
+
+  @param[in] MwaitSupport    TRUE indicates MONITOR is supported.
+                             FALSE indicates MONITOR is not supported.
+  @param[in] ApTargetCState  Target C-State value.
+  @param[in] PmCodeSegment   Protected mode code segment value.
+**/
+typedef
+VOID
+(EFIAPI * ASM_RELOCATE_AP_LOOP) (
+  IN BOOLEAN                 MwaitSupport,
+  IN UINTN                   ApTargetCState,
+  IN UINTN                   PmCodeSegment
+  );
 #endif