layers: Add tracking for VK_KHR_display extension in PV

Signed-off-by: Chris Forbes <chrisforbes@google.com>
diff --git a/layers/parameter_validation_utils.h b/layers/parameter_validation_utils.h
index a3aa113..9e99964 100644
--- a/layers/parameter_validation_utils.h
+++ b/layers/parameter_validation_utils.h
@@ -80,6 +80,7 @@
     bool mir_enabled;
     bool android_enabled;
     bool win32_enabled;
+    bool display_enabled;
 };
 
 // String returned by string_VkStructureType for an unrecognized type.