StandaloneMmPkg/Core: Print discovered drivers that weren't dispatched

This is very useful debugging information. It often helps debug where
driver load failures started, which dependency was unmet.

Perhaps this was commented out while the standalone MM core was
developed.

Signed-off-by: Benjamin Doron <benjamin.doron@9elements.com>

StandaloneMmPkg/Core/StandaloneMmCore.c

@@ -265,7 +265,9 @@ MmReadyToLockHandler (
   // Display any drivers that were not dispatched because dependency expression
   // evaluated to false if this is a debug build
   //
-  // MmDisplayDiscoveredNotDispatched ();
+  DEBUG_CODE_BEGIN ();
+  MmDisplayDiscoveredNotDispatched ();
+  DEBUG_CODE_END ();
 
   return Status;
 }