MdePkg: Do not use CreateEventEx unless required

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=2446

There are many firmwares in the wild not supporting CreateEventEx,
including devices less than 5 years old.

Signed-off-by: Vitaly Cheptsov <vit9696@protonmail.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>

MdePkg/Library/UefiDebugLibDebugPortProtocol/DebugLibConstructor.c

@@ -64,12 +64,11 @@ DxeDebugLibConstructor(
 {
   mDebugBS = SystemTable->BootServices;
 
-  mDebugBS->CreateEventEx (
-              EVT_NOTIFY_SIGNAL,
+  mDebugBS->CreateEvent (
+              EVT_SIGNAL_EXIT_BOOT_SERVICES,
               TPL_NOTIFY,
               ExitBootServicesCallback,
               NULL,
-              &gEfiEventExitBootServicesGuid,
               &mExitBootServicesEvent
               );
 

MdePkg/Library/UefiDebugLibDebugPortProtocol/UefiDebugLibDebugPortProtocol.inf

@@ -46,9 +46,6 @@
   PrintLib
   DebugPrintErrorLevelLib
 
-[Guids]
-  gEfiEventExitBootServicesGuid                 ## CONSUMES
-
 [Protocols]
   gEfiDebugPortProtocolGuid                     ## CONSUMES