MdePkg/UefiDebugLibDebugPortProtocol: Add destructor to CloseEvent

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=2012

When driver is unloaded, the ExitBootSerivesEvent must be closed at
the same time. Otherwise exception will occur when ExitBootServices.

Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Signed-off-by: Wei6 Xu <wei6.xu@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>

MdePkg/Library/UefiDebugLibDebugPortProtocol/DebugLibConstructor.c

@@ -75,3 +75,26 @@ DxeDebugLibConstructor(
 
   return EFI_SUCCESS;
 }
+
+/**
+  The destructor closes Exit Boot Services Event.
+
+  @param  ImageHandle   The firmware allocated handle for the EFI image.
+  @param  SystemTable   A pointer to the EFI System Table.
+
+  @retval EFI_SUCCESS   The destructor always returns EFI_SUCCESS.
+
+**/
+EFI_STATUS
+EFIAPI
+DxeDebugLibDestructor(
+  IN EFI_HANDLE                 ImageHandle,
+  IN EFI_SYSTEM_TABLE           *SystemTable
+  )
+{
+  if (mExitBootServicesEvent != NULL) {
+    SystemTable->BootServices->CloseEvent (mExitBootServicesEvent);
+  }
+
+  return EFI_SUCCESS;
+}

MdePkg/Library/UefiDebugLibDebugPortProtocol/UefiDebugLibDebugPortProtocol.inf

@@ -22,6 +22,7 @@
   LIBRARY_CLASS                  = DebugLib|DXE_CORE DXE_DRIVER DXE_RUNTIME_DRIVER UEFI_APPLICATION UEFI_DRIVER
 
   CONSTRUCTOR                    = DxeDebugLibConstructor
+  DESTRUCTOR                     = DxeDebugLibDestructor
 
 #
 #  VALID_ARCHITECTURES           = IA32 X64 EBC