Add missing routine declaration

xtldr/includes/xtbl.h

@@ -50,6 +50,10 @@ BlDbgPrint(IN PUINT16 Format,
 INT_PTR
 BlEfiGetSecureBootStatus();
 
+EFI_STATUS
+BlEfiGetSystemConfigurationTable(IN PEFI_GUID TableGuid,
+                                 OUT PVOID *Table);
+
 EFI_STATUS
 BlEfiMemoryAllocatePool(IN UINT_PTR Size,
                         OUT PVOID *Memory);