bug-14538: Remove validation error codes

https://cvs.khronos.org/bugzilla/show_bug.cgi?id=14538
diff --git a/layers/shader_checker.cpp b/layers/shader_checker.cpp
index 632947a..678b567 100644
--- a/layers/shader_checker.cpp
+++ b/layers/shader_checker.cpp
@@ -976,7 +976,7 @@
         return get_dispatch_table(shader_checker_device_table_map, device)->CreateGraphicsPipelines(device, pipelineCache, count, pCreateInfos, pPipelines);
     }
     else {
-        return VK_ERROR_UNKNOWN;
+        return VK_ERROR_VALIDATION_FAILED;
     }
 }